Optical compensatory sheet comprising substrate, orientation layer and optically anisotropic layer

ABSTRACT

An optical compensatory sheet comprises a transparent substrate, an orientation layer and an optically anisotropic layer in order. The optically anisotropic layer comprises discotic liquid crystal molecules. The orientation layer comprises a denatured polyvinyl alcohol having a hydrocarbon group containing 10 to 100 carbon atoms or a denatured polyvinyl alcohol containing fluorine atoms. The discotic liquid crystal molecules are aligned at an average inclined angle in the range of 50° to 90°. An orientation layer, a liquid crystal display of an STN mode and a method of alignment of discotic liquid crystal molecules are also disclosed.

FIELD OF THE INVENTION

The present invention relates to an optical compensatory sheetcomprising a transparent substrate, an orientation layer and anoptically anisotropic layer comprising discotic liquid crystal moleculesin order. The invention also relates to an orientation layer for liquidcrystal. The invention further relates to a liquid crystal display of anSTN mode. The invention furthermore relates to a process of alignment ofdiscotic liquid crystal molecules at an average inclined angle in therange of 50° to 90°.

BACKGROUND OF THE INVENTION

A liquid crystal display of an STN mode comprises a liquid crystal cellof an STN (Super Twisted Nematic) mode, two polarizing elements arrangedon each side of the liquid crystal cell, and one or two opticalcompensatory sheets (phase retarders) arranged between the liquidcrystal cell and the polarizing element.

The liquid crystal cell comprises a pair of substrates, rod-like liquidcrystal molecules and an electrode layer. The rod-like liquid crystalmolecules are provided between the substrates. The electrode layer has afunction of applying a voltage to the rod-like liquid crystal molecule.Each of the substrates has an orientation layer, which has a function ofaligning the rod-like liquid crystal molecule. The rod-like liquidcrystal molecules are twisted by using a chiral agent. A twist angle ofthe molecules is in the range of 90° to 360°.

Without use of an optical compensatory sheet, a liquid crystal displayof an STN mode displays an image colored blue or yellow because ofbirefringence of rod-like liquid crystal molecules. The blue or yellowcolor is inconvenient for not only a black and white image but also acolor image. An optical compensatory sheet has a function of removingcolor from an image to display a bright and clear image. The opticalcompensatory sheet also has a function of enlarging a viewing angle of aliquid crystal cell. A stretched birefringent film has usually been usedas the optical compensatory sheet. Japanese Patent ProvisionalPublication Nos. 7(1995)-104284 and 7(1995)-13021 disclose an opticalcompensatory sheet made of a stretched birefringent film for a liquidcrystal display of an STN mode.

An optical compensatory sheet comprising an optically anisotropic layeron a transparent substrate has been proposed to be used in place of thestretched birefringent film. The optically anisotropic layer is formedby aligning discotic liquid crystal molecules and fixing the alignedmolecules. The discotic liquid crystal molecules usually have largebirefringence. The discotic liquid crystal molecules also have variousalignment forms. Accordingly, an optical compensatory sheet obtained byusing the discotic liquid crystal molecule has a specific opticalcharacteristic that cannot be obtained by the conventional stretchedbirefringent film. The optical compensatory sheet using the discoticliquid crystal molecule is disclosed in Japanese Patent ProvisionalPublication No. 6(1994)-214116, U.S. Pat. Nos. 5,583,679, 5,646,703 andGerman Patent Publication No. 3,911,620A1. However, the disclosedoptical compensatory sheet is designed to be used in a liquid crystaldisplay of a TN (Twisted Nematic) mode.

The optical compensatory sheet containing the discotic liquid crystalmolecules should be redesigned to be used in a liquid crystal display ofan STN mode. In a liquid crystal cell of the STN mode, rod-like liquidcrystal molecules are aligned according to a super twisted birefringentmode at a twist angle of larger than 90°. The liquid crystal display ofthe STN mode can display a clear image of a large volume according to atime-sharing addressing method even though the display has a simplematrix electrode structure (having no active matrix such as a thin filmtransistor or a diode).

The discotic liquid crystal molecules should be essentially verticallyaligned (homogeneously aligned) to optically compensate the liquidcrystal cell of the STN mode. The discotic liquid crystal molecules arepreferably further twisted. Japanese Patent Provisional Publication No.9(1997)-26572 discloses an optical compensatory sheet in which discoticliquid crystal molecules are twisted. The drawings of Japanese PatentProvisional Publication No. 9(1997)-26572 further illustrate thatdiscotic liquid crystal molecules are essentially vertically aligned.

SUMMARY OF THE INVENTION

It is technically difficult to align discotic liquid crystal moleculesuniformly (monodomain alignment) from an interface facing an orientationlayer to another interface facing the air according to the disclosuresof Japanese Patent Provisional Publication No. 9(1997)-26572. If thediscotic liquid crystal molecules are not uniformly aligned,disclination of the molecules causes scattered light, which decreases acontrast ratio of a displayed image.

Rod-like liquid crystal molecules-used in a liquid crystal cell havebeen investigated to align the molecule essentially vertically(homeotropic alignment). For example, a liquid crystal display of avertical alignment (VA) mode uses an orientation layer having a functionof essentially vertically aligning rod-like liquid crystal molecules. Inthe liquid crystal display of the VA mode, rod-like liquid crystalmolecules are essentially vertically aligned while not applying voltageto the cell, and are essentially horizontally aligned while applyingvoltage to the cell. Various orientation layers have been proposed toalign rod-like liquid crystal molecules.

Discotic liquid crystal molecules are completely different from therod-like liquid crystal molecules in molecular structures and in opticalcharacteristics. Most of the orientation layers having a function ofaligning rod-like liquid crystal molecules are not effective in aligningdiscotic liquid crystal molecules.

An object of the present invention is to provide an optical compensatorysheet suitable for a liquid crystal display of an STN mode.

Another object of the invention is to provide an orientation layerhaving a function of aligning liquid crystal molecule (particularlydiscotic liquid crystal molecules) vertically.

A further object of the invention is to provide a liquid crystal displayof an STN mode that can display a clear image of a high contrast, inwhich blue or yellow color caused by birefringence of rod-like liquidcrystal molecule is reduced.

A furthermore object of the invention is to provide a method forvertical, uniform and stable alignment of discotic liquid crystalmolecules.

The present invention provides an optical compensatory sheet comprisinga transparent substrate, an orientation layer and an opticallyanisotropic layer in order, said optically anisotropic layer comprisingdiscotic liquid crystal molecules, wherein the orientation layercomprises a denatured polyvinyl alcohol having a hydrocarbon groupcontaining 10 to 100 carbon atoms, said discotic liquid crystalmolecules being aligned at an average inclined angle in the range of 50°to 90°.

The invention further provides an orientation layer provided on asupport, said orientation layer having a function of aligning liquidcrystal, wherein the orientation layer comprises a denatured polyvinylalcohol having a hydrocarbon group containing 10 to 100 carbon atoms.

The invention furthermore provides a liquid crystal display comprising aliquid crystal cell of an STN mode, two polarizing elements arranged oneach side of the liquid crystal cell and one or two optical compensatorysheets arranged between the liquid crystal cell and the polarizingelements, wherein the optical compensatory sheet comprises a transparentsubstrate, an orientation layer and an optically anisotropic layer inorder, said transparent substrate being adjacent to the polarizingelement, said optically anisotropic layer comprising discotic liquidcrystal molecules, said orientation layer comprising a denaturedpolyvinyl alcohol having a hydrocarbon group containing 10 to 100 carbonatoms, and said discotic liquid crystal molecules being aligned at anaverage inclined angle in the range of 50° to 90°.

The invention still furthermore provides a method of alignment ofdiscotic liquid crystal molecules, which comprises forming an opticallyanisotropic layer comprising discotic liquid crystal molecules on anorientation layer comprising a denatured polyvinyl alcohol having ahydrocarbon group containing 10 to 100 carbon atoms to align thediscotic liquid crystal molecules at an average inclined angle in therange of 50° to 90°.

The invention also provides an optical compensatory sheet comprising atransparent substrate, an orientation layer and an optically anisotropiclayer in order, said optically anisotropic layer comprising discoticliquid crystal molecules, wherein the orientation layer comprises adenatured polyvinyl alcohol containing fluorine atoms, said discoticliquid crystal molecules being aligned at an average inclined angle inthe range of 50° to 90°.

The invention further provides an orientation layer provided on asupport, said orientation layer having a function of aligning liquidcrystal, wherein the orientation layer comprises a denatured polyvinylalcohol containing fluorine atoms.

The invention furthermore provides a liquid crystal display comprising aliquid crystal cell of an STN mode, two polarizing elements arranged oneach side of the liquid crystal cell and one or two optical compensatorysheets arranged between the liquid crystal cell and the polarizingelements, wherein the optical compensatory sheet comprises a transparentsubstrate, an orientation layer and an optically anisotropic layer inorder, said transparent substrate being adjacent to the polarizingelement, said optically anisotropic layer comprising discotic liquidcrystal molecules, said orientation layer comprising a denaturedpolyvinyl alcohol containing fluorine atoms, and said discotic liquidcrystal molecules being aligned at an average inclined angle in therange of 50° to 90°.

The invention still furthermore provides a method of alignment ofdiscotic liquid crystal molecules, which comprises forming an opticallyanisotropic layer comprising discotic liquid crystal molecules on anorientation layer comprising a denatured polyvinyl alcohol containingfluorine atoms to align the discotic liquid crystal molecules at anaverage inclined angle in the range of 50° to 90°.

In the present specification, the term “average inclined angle” means anaverage of angles between discotic planes of discotic liquid crystalmolecules (or long axes of rod-like liquid crystal molecules) and asurface of a transparent substrate (or a surface of an orientationlayer). The present specification refers to alignment of liquid crystalmolecules at an average inclined angle in the range of 50° to 90° asessentially vertical alignment of the molecules.

The applicants have succeeded in obtaining essentially vertical, uniformand stable alignment of liquid crystal molecules by using an orientationlayer comprising a denatured polyvinyl alcohol having a hydrocarbongroup containing 10 to 100 carbon atoms or a denatured polyvinyl alcoholcontaining fluorine atoms. The orientation layer is particularlyeffective in aligning discotic liquid crystal molecule.

An optical compensatory sheet suitable for a liquid crystal display ofan STN mode is now obtained by using the discotic liquid crystalmolecules of the essentially vertical, uniform and stable alignment.Thus, blue or yellow color is reduced in a liquid crystal display of anSTN mode to display a clear image of a high contrast by using an opticalcompensatory sheet, in which the discotic liquid crystal molecules areessentially vertically aligned (and preferably twisted).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view schematically illustrating alignment ofrod-like liquid crystal molecules in a liquid crystal cell of an STNmode and alignment of discotic liquid crystal molecules in an opticallyanisotropic layer when voltage is not applied (off) to the cell.

FIG. 2 schematically illustrates a refractive index ellipsoid of arod-like liquid crystal molecule in a liquid crystal cell and arefractive index ellipsoid of a discotic liquid crystal molecule in anoptical anisotropic layer, which optically compensates the rod-likeliquid crystal molecule.

FIGS. 3(a)-(e) schematically illustrate a layered structure of a liquidcrystal display of an STN mode.

FIGS. 4(a)-(e) are plane views showing preferred optical directionsabout elements of a liquid crystal display of an STN mode.

FIGS. 5(a)-(e) are plane views showing other preferred opticaldirections about elements of a liquid crystal display of an STN mode.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a sectional view schematically illustrating alignment ofrod-like liquid crystal molecules in a liquid crystal cell of an STNmode and alignment of discotic liquid crystal molecules in an opticallyanisotropic layer when voltage is not applied (off) to the cell.

As is shown in FIG. 1, a liquid crystal cell (11 to 15) comprises anupper substrate (11) having an upper orientation layer (12), a lowersubstrate (15) having a lower orientation layer (14) and a liquidcrystal layer comprising rod-like liquid crystal molecules (13 a to 13e) sealed between the orientation layers (12 & 14). The rod-like liquidcrystal molecules (13 a to 13 e) are aligned by functions of theorientation layers (12 & 14), and are twisted by a function of a chiralagent (not shown) contained in the liquid crystal layer.

Each of the upper substrate (11) and the lower substrate (15) has anelectrode (not shown), which has a function of applying voltage to therod-like liquid crystal molecules (13 a to 13 e).

When voltage is not applied to the liquid crystal cell of an STN mode(off), the rod-like liquid crystal molecules (13 a to 13 e) areessentially horizontally aligned parallel to the surface of theorientation layers (12 & 14), as is shown in FIG. 1. The rod-like liquidcrystal molecules (13 a to 13 e) are twisted along a thicknessdirection, and spiral on a plane (counterclockwise about 240° from 13 ato 13 e in FIG. 1).

When voltage is applied to the liquid crystal cell of an STN mode (on),rod-like liquid crystal molecules placed in the middle of the cell (13 bto 13 d) are rather vertically aligned (realigned parallel to adirection of an electric field), compared with FIG. 1 (off). On theother hand, the alignment of the other rod-like liquid crystal molecules(13 a, 13 e) neighboring the substrates (11, 15) is not essentiallychanged after applying voltage to the cell.

An optical compensatory sheet is provided under the liquid crystal cell.The optical compensatory sheet shown in FIG. 1 comprises a transparentsubstrate (23), an orientation layer (22) and an optically anisotropiclayer in order. The optically anisotropic layer is formed by aligningdiscotic liquid crystal molecules (21 a to 21 e) and fixing themolecules while keeping the alignment.

According to the present invention, discotic liquid crystal molecules(21 a to 21 e) are so aligned that discotic planes of the molecules areessentially perpendicular to a surface of the orientation layer (22).The discotic liquid crystal molecules (21 a to 21 e) are preferablytwisted along a thickness direction, and spiral on a plane (clockwiseabout 240° from 21 a to 21 e in FIG. 1).

In FIG. 1, alignment of each of the rod-like liquid crystal moleculescorresponds to alignment of each of the discotic liquid crystalmolecules, namely 13 a to 21 e, 13 b to 21 d, 13 c to 21 c, 13 d to 21 band 13 e to 21 a.

Accordingly, the discotic liquid crystal molecule 21 e opticallycompensates the rod-like liquid crystal molecule 13 a, 21 d compensates13 b, 21 c compensates 13 c, 21 b compensates 13 d, and 21 a compensates13 e. The optical relation between the rod-like liquid crystal moleculeand the discotic liquid crystal molecule is described below referring toFIG. 2.

FIG. 2 schematically illustrates a refractive index ellipsoid of arod-like liquid crystal molecule in a liquid crystal cell and arefractive index ellipsoid of a discotic liquid crystal molecule in anoptical anisotropic layer, which optically compensates the rod-likeliquid crystal molecule.

The refractive index ellipsoid (13) of a rod-like liquid crystalmolecule in a liquid crystal cell is formed by refractive indices (13 x,13 y) in plane parallel to an orientation layer and a refractive index(13 z) along a thickness direction. In a liquid crystal cell of an STNmode, the refractive index (13 x) along one direction in place isrelatively large, while the index (13 y) along a direction perpendicularto the direction of (13 x) is relatively small. The refractive index (13z) along the direction is also relatively small in a liquid crystal cellof an STN mode. Therefore, the refractive index ellipsoid (13) has ashape like a laid football, as is shown in FIG. 2. The liquid crystalcell having the refractive index ellipsoid (not spherical) shows abirefringence depending on a viewing angle. The dependency on theviewing angle is canceled by an optical compensatory sheet.

The refractive index ellipsoid (21) of a discotic liquid crystalmolecule in an optical compensatory sheet is also formed by refractiveindices (21 x, 21 y) in plane parallel to an orientation layer and arefractive index (21 z) along a thickness direction. The refractiveindex (21 x) along one direction in place is relatively small, while theindex (21 y) along a direction perpendicular to the direction of (21 x)is relatively small. The refractive index (121 z) along the direction isalso relatively large. These refractive indices are obtained by aligninga discotic liquid crystal molecule essentially vertically. Therefore,the refractive index ellipsoid (21) has a shape like a standing disk, asis shown in FIG. 2.

A retardation formed in a liquid crystal cell (1) can be compensated bya retardation formed in an optical compensatory sheet (2) because of theabove-described relation. The dependency on a viewing angle of theliquid crystal cell can be canceled by adjusting optical characteristicsof a rod-like liquid crystal molecule and a discotic liquid crystalmolecule that has a director having the same direction as the directorof the rod-like liquid crystal molecule. In more detail, the dependencyon a viewing angle can be canceled by adjusting refractive indices (13x, 13 y, 13 z) of a rod-like liquid crystal molecule, refractive indices(21 x, 21 y, 21 z) of a discotic liquid crystal molecule, a thickness(13 t) of the rod-like liquid crystal molecule layer and a thickness (21t) of the discotic liquid crystal molecule layer according to thefollowing formulas.

|(13 x−13 y)×13 t|=|(21 x−21 y)×21 t|

|(13 x−13 z)×13 t|=|(21 x−21 z)×21 t|

FIG. 3 schematically illustrates a layered structure of a liquid crystaldisplay of an STN mode.

The liquid crystal display shown in FIG. 3(a) comprises a backlight(BL), a lower polarizing element (3 a), a lower optical compensatorysheet (2 a), a liquid crystal cell of an STN mode (1) and an upperpolarizing element (3 b) in order.

The liquid crystal display shown in FIG. 3(b) comprises a backlight(BL), a lower polarizing element (3 a), a lower optical compensatorysheet (2 a), an upper optical compensatory sheet (2 b), a liquid crystalcell of an STN mode (1) and an upper polarizing element (3 b) in order.

The liquid crystal display shown in FIG. 3(c) comprises a backlight(BL), a lower polarizing element (3 a), a liquid crystal cell of an STNmode (1), an upper optical compensatory sheet (2 b) and an upperpolarizing element (3 b) in order.

The liquid crystal display shown in FIG. 3(d) comprises a backlight(BL), a lower polarizing element (3 a), a liquid crystal cell of an STNmode (1), a lower optical compensatory sheet (2 a), an upper opticalcompensatory sheet (2 b) and an upper polarizing element (3 b) in order.

The liquid crystal display shown in FIG. 3(e) comprises a backlight(BL), a lower polarizing element (3 a), a lower optical compensatorysheet (2 a), a liquid crystal cell of an STN mode (1), an upper opticalcompensatory sheet (2 b) and an upper polarizing element (3 b) in order.

FIG. 3 shows arrows, which indicate the following optical directions.

TAa: Transparent axis (TAa) of a lower polarizing element (3 a)

DDa: Normal (director's) direction of a discotic plane of a discoticliquid crystal molecule adjacent to an orientation layer in a loweroptical compensatory sheet (2 a)

DDb: Normal (director's) direction of a discotic plane of a discoticliquid crystal molecule adjacent to a liquid crystal cell in a loweroptical compensatory sheet (2 a)

RDa: Rubbing direction of a lower orientation layer of a liquid crystalcell (1)

RDb: Rubbing direction of an upper orientation layer of a liquid crystalcell (1)

DDc: Normal (director's) direction of a discotic plane of a discoticliquid crystal molecule adjacent to a liquid crystal cell in an upperoptical compensatory sheet (2 b)

DDd: Normal (director's) direction of a discotic plane of a discoticliquid crystal molecule adjacent to an orientation layer in an upperoptical compensatory sheet (2b)

TAa: Transparent axis (TAa) of an upper polarizing element (3b)

The angles between the optical directions are described below referringto FIG. 4 and FIG. 5.

FIG. 4 is a plane view showing preferred optical directions aboutelements of a liquid crystal display of an STN mode. FIG. 4 showsarrangements taking account of a front contrast.

FIG. 4(a) shows a liquid crystal display comprising one opticalcompensatory sheet between a lower polarizing element and a liquidcrystal cell of an STN mode, as is shown in FIG. 3(a).

FIG. 4(b) shows a liquid crystal display comprising two opticalcompensatory sheets between a lower polarizing element and a liquidcrystal cell of an STN mode, as is shown in FIG. 3(b).

FIG. 4(c) shows a liquid crystal display comprising one opticalcompensatory sheet between a liquid crystal cell of an STN mode and anupper polarizing element, as is shown in FIG. 3(c).

FIG. 4(d) shows a liquid crystal display comprising two opticalcompensatory sheets between a liquid crystal cell of an STN mode and anupper polarizing element, as is shown in FIG. 3(d).

FIG. 4(e) shows a liquid crystal display comprising one opticalcompensatory sheet between a lower polarizing element and a liquidcrystal display of an STN mode, and another optical compensatory sheetbetween the liquid crystal cell and an upper polarizing element, as isshown in FIG. 3(e).

In FIG. 4, the line (X) means a standard direction (0°). The arrowsshown in FIG. 4 have the same meanings as is described about FIG. 3. Thetransparent axis of the lower polarizing element (TAa) and thetransparent axis of the upper polarizing element (TAb) can be replacedwith each other.

FIG. 5 is a plane view showing other preferred optical directions aboutelements of a liquid crystal display of an STN mode. FIG. 5 showsarrangements taking account of color of a displayed image.

FIG. 5(a) shows a liquid crystal display comprising one opticalcompensatory sheet between a lower polarizing element and a liquidcrystal cell of an STN mode, as is shown in FIG. 3(a).

FIG. 5(b) shows a liquid crystal display comprising two opticalcompensatory sheets between a lower polarizing element and a liquidcrystal cell of an STN mode, as is shown in FIG. 3(b).

FIG. 5(c) shows a liquid crystal display comprising one opticalcompensatory sheet between a liquid crystal cell of an STN mode and anupper polarizing element, as is shown in FIG. 3(c). FIG. 5(d) shows aliquid crystal display comprising two optical compensatory sheetsbetween a liquid crystal cell of an STN mode and an upper polarizingelement, as is shown in FIG. 3(d).

FIG. 5(e) shows a liquid crystal display comprising one opticalcompensatory sheet between a lower polarizing element and a liquidcrystal display of an STN mode, and another optical compensatory sheetbetween the liquid crystal cell and an upper polarizing element, as isshown in FIG. 3(e).

In FIG. 5, the line (X) means a standard direction (0°). The arrowsshown in FIG. 5 have the same meanings as is described about FIG. 3. Thetransparent axis of the lower polarizing element (TAa) and thetransparent axis of the upper polarizing element (TAb) can be replacedwith each other.

[Transparent Substrate]

A transparent substrate is preferably made of a polymer film, which morepreferably is optical isotropic. The term “transparent” means that lighttransmittance is not less than 80%. The term “optical isotropic” meansthat a retardation in plane (Re) of the film is not more than 20 nm,preferably not more than 10 nm, and more preferably not more than 5 nm.A retardation along a thickness direction (Rth) of the film ispreferably not more than 100 nm, more preferably not more than 50 nm,and most preferably not more than 30 nm. The Re and Rth retardationvalues are defined by the following formulas.

Re=(nx−ny)×d

Rth=[{(nx+ny)/2}−nz]×d

in which each of nx and ny is a refractive index in plane of thetransparent substrate; nz is a refractive index along a thicknessdirection of the transparent substrate; and d is a thickness of atransparent substrate.

Examples of the polymers include cellulose ester, polycarbonate,polysulfone, polyethersulfone, polyacrylate and polymethacrylate.Cellulose ester is preferred, cellulose acetate is more preferred, andcellulose triacetate is most preferred. The polymer film is formedpreferably according to a solvent casting method.

The transparent substrate has a thickness preferably in the range of 20to 500 μm, and more preferably in the range of 50 to 200 μm.

The transparent substrate can be subjected to a surface treatment (e.g.,glow discharge treatment, corona discharge treatment, ultraviolet (UV)treatment, flame treatment) to improve adhesion to a layer formed on thesubstrate (e.g., adhesive layer, orientation layer, opticallyanisotropic layer). An adhesive layer (undercoating layer) can beprovided on the transparent substrate.

[Orientation Layer]

In the present invention, the orientation layer comprises a denaturedpolyvinyl alcohol having a hydrocarbon group containing 10 to 100 carbonatoms or a denatured polyvinyl alcohol containing fluorine atoms. Thehydrocarbon group or the fluorine atoms are preferably present at a sidechain of the denatured polyvinyl alcohol.

According to study of the applicants, liquid crystal molecules(particularly discotic liquid crystal molecules) can be essentiallyvertically aligned by a function of a side chain (rather than a mainchain) of a polymer contained in an orientation layer. A functionalgroup of the side chain decreases a surface energy of the orientationlayer to erect a liquid crystal molecule. A hydrocarbon group containing10 to 100 carbon atoms can be effectively used as the functional group.Fluorine atom can also be effectively used as the functional group. Thehydrocarbon group or fluorine atom is introduced into a side chain of apolymer to arrange the group or the atom on the surface of theorientation layer.

The hydrocarbon group is an aliphatic group, an aromatic group or acombination thereof. The aliphatic group can have a branched or cyclicstructure. The aliphatic group preferably is an alkyl group (including acycloalkyl group) or an alkenyl group (including a cycloalkenyl group).The hydrocarbon group can have a substituent group that is not stronglyhydrophilic, such as a halogen atom. The hydrocarbon group contains 10to 100 carbon atoms, preferably 10 to 60 carbon atoms, and morepreferably 10 to 40 carbon atoms.

The hydrocarbon group preferably has a steroid structure. The steroidstructure has an excluded volume effect as well as the above-describedfunction of decreasing a surface energy of the orientation layer. Liquidcrystal molecules can be strongly elected by the combination of theexcluded volume effect and the function of decreasing the surfaceenergy. In the present specification, the steroid structure means acyclopentanohydrophenanthrene ring or a ring obtained by replacing asingle bond of the cyclopentanohydrophenanthrene ring with a double bondso long as the ring is aliphatic (not forming an aromatic ring). Thehydrocarbon group having the steroid structure preferably contains 18 to100 carbon atoms, more preferably contains 19 to 60 carbon atoms, andmost preferably contains 20 to 40 carbon atoms.

The fluorine atom is preferably present as a substituent group of ahydrocarbon side chain of a repeating unit of a denatured polyvinylalcohol.

The denatured polyvinyl alcohol having a hydrocarbon group compriseshydrocarbon repeating units preferably in an amount of 2 to 80 mol %,and more preferably in an amount of 3 to 70 mol %. The repeating unithas a hydrocarbon group containing 10 to 100 carbon atoms.

A preferred denatured polyvinyl alcohol having a hydrocarbon group isrepresented by the formula (PVc):

-(VAl)_(x)-(HyC)_(y)-(VAc)_(z)—  (PVc)

in which VAl is a vinyl alcohol repeating unit; Hyc is a repeating unithaving a hydrocarbon group containing 10 to 100 carbon atoms; VAc is avinyl acetate repeating unit; x is 20 to 90 mol % (preferably 25 to 90mol %); y is 2 to 80 mol % (preferably 3 to 70 mol %); and z is 0 to 30mol % (preferably 2 to 20 mol %).

Preferred repeating units having a hydrocarbon group containing 10 to100 carbon atoms (HyC) are represented by the formulas (HyC-I) and(HyC-II):

in which L¹ is a divalent linking group selected from the groupconsisting of —O—, —CO—, —SO₂—, —NH—, -alkylene-, -arylene- and acombination thereof; L² is a single bond or a divalent linking groupselected from the group consisting of —O—, —CO—, —SO₂—, —NH—,-alkylene-, -arylene- and a combination thereof; and each of R¹ and R²is a hydrocarbon group containing 10 to 100 carbon atoms.

Examples of the divalent linking groups formed by the combinations areshown below.

L1: —O—CO—

L2: —O—CO-alkylene-O—

L3: —O—CO-alkylene-CO—NH—

L4: —O—CO-alkylene-NH—SO₂-arylene-O—

L5: -arylene-NH—CO—

L6: -arylene-CO—O—

L7: -arylene-CO—NH—

L8: -arylene-O—

L9: —O—CO—NH-arylene-NH—CO—

L10: —O—CO—C—

L11: —O—SO₂—

L12: —O—CO—NH-arylene-O—

L13: —O—CO—O-alkylene-CO—

L14: -alkylene-CO—O—

L15: —O—CO—NH-alkylene-NH—CO—O—

L16: —O—CO—NH-arylene-CO—(O-alkylene-)_(n)—O—

(n: an integer of 1 to 10)

Examples of the repeating units having a hydrocarbon group containing 10to 100 carbon atoms are shown below.

A specific group other than the hydrocarbon repeating units can beattached to the end of the denatured polyvinyl alcohol. Examples of theend groups include an alkylthio group.

Examples of the denatured polyvinyl alcohol having hydrocarbon groupscontaining 10 to 100 carbon atoms are shown below. The ratio of therepeating unit means mol %.

PV1: -(VAl)₈₀-(HyC1)₈-(VAc)₁₂-

PV2: -(VAl)₆₉-(HyC1)₁₉-(VAc)₁₂-

PV3: -(VAl)₆₈-(HyC2)₂₀-(VAc)₁₂-

PV4: -(VAl)₈₁-(HyC2)₁₇-(VAc)₂-

PV5: -(VAl)₆₈-(HyC3)₂₀-(VAc)₁₂-

PV6: -(VAl)₇₀-(HyC3)₁₅-(VAc)₁₈-

PV7: -(VAl)₇₄-(HyC4)₂₀-(VAc)₆-

PV8: -(VAl)₆₃-(HyC4)₂₅-(VAc)₁₂-

PV9: -(VAl)₇₀-(HyC4)₁₀-(VAc)₂₀-

PV10: -(VAl)₈₃-(HyC5)₅-(VAc)₁₂-

PV11: -(VAl)₈₅-(HyC5)₃-(VAc)₁₂-

PV12: -(VAl)₉₀-(HyC5)₈-(VAc)₂-

PV13: -(VAl)₇₈-(HyC6)₁₀-(VAc)₁₂-

PV14: -(VAl)₈₅-(HyC6)₁₃-(VAc)₂-

PV15: -(VAl)₆₇-(HyC6)₂₁-(VAc)₁₂-

PV16: -(VAl)₇₂-(HyC7)₁₆-(VAc)₁₂-

PV17: -(VA)₈₁-(HyC7)₁₃-(VAc)₆-

PV18: -(VAl)₇₇-(HyC7)₂₁-(VAc)₂-

PV19: -(VAl)₇₀-(HyC8)₂₂-(VAc)₈-

PV20: -(VAl)₆₇-(HyC8)₁₁-(VAc)₁₂-

PV21: -(VAl)₇₀-(HyC8)₂₈-(VAc)₂-

PV22: -(VAl)₆₃-(HyC9)₃₅-(VAc)₂-

PV23: -(VAl)₆₈-(HyC9)₂₄-(VAc)₈-

PV24: -(VAl)₇₆-(HyC9)₁₂-(VAc)₁₂-

PV25: -(VAl)₇₆-(HyC10)₁₂-(VAc)₁₂-S-n-C₁₂H₂₅

PV26: -(VAl)₇₃-(HyC10)₁₅-(VAc)₁₂-S-n-C₁₂H₂₅

PV27: -(VAl)₈₁-(HyC10)₇-(VAc)₁₂-S-n-C₁₂H₂₅

PV28: -(VAl)₇₅-(HyC11)₁₉-(VAc)₆-

PV29: -(VAl)₇₅-(HyC11)₂₃-(VAc)₂-

PV30: -(VAl)₈₀-(HyC11)₁₈-(VAc)₂-

PV31: -(VAl)₆₈-(HyC12)₂₄-(VAc)₈-

PV32: -(VAl)₅₅-(HyC12)₃₃-(VAc)₁₂-

PV33: -(VAl)₆₈-(HyC12)₂₀-(VAc)₁₂-

PV34: -(VAl)₆₈-(HyC13)₂₀-(VAc)₁₂-

PV35: -(VAl)₇₃-(HyC13)₁₅-(VAc)₁₂-

PV36: -(VAl)₇₈-(HyC13)₁₀-(VAc)₁₂-

PV37: -(VAl)₅₃-(HyC14)₃₅-(VAc)₁₂-

PV38: -(VAl)₆₄-(HyC14)₃₀-(VAc)₆-

PV39: -(VAl)₇₃-(HyC14)₂₅-(VAc)₂-

PV40: -(VAl)₇₄-(HyC15)₁₄-(VAc)₁₂-

PV41: -(VAl)₃₈-(HyC15)₅₀-(VAc)₁₂-

PV42: -(VAl)₂₇-(HyC15)₆₅-(VAc)₈-

PV43: -(VAl)₇₂-(HyC16)₂₆-(VAc)₂-

PV44: -(VAl)₆₁-(HyC16)₃₁-(VAc)₈-

PV45: -(VAl)₇₂-(HyC16)₁₆-(VAc)₁₂-

PV46: -(VAl)₅₅-(HyC17)₃₃-(VAc)₁₂-

PV47: -(VAl)₃₂-(HyC17)₅₆-(VAc)₁₂-

PV48: -(VAl)₂₈-(HyC17)₇₀-(VAc)₈-

PV49: -(VAl)₆₃-(HyC18)₂₅-(VAc)₁₂-

PV50: -(VAl)₇₄-(HyC18)₂₀-(VAc)₆-

PV51: -(VAl)₈₃-(HyC18)₁₅-(VAc)₂-

PV52: -(VAl)₆₅-(HyC19)₃₁-(VAc)₂-S-n-C₁₂H₂₅

PV53: -(VAl)₅₁-(HyC19)₄₇-(VAc)₂-S-n-C₁₂H₂₅

PV54: -(VAl)₇₂-(HyC19)₂₀-(VAc)₈-S-n-C₁₂H₂₅

PV101: -(VAl)₈₀-(HyC21)₈-(VAc)₁₂-

PV102: -(VAl)₆₉-(HyC21)₁₉-(VAc)₁₂-

PV103: -(VAl)₆₈-(HyC22)₂₀-(VAc)₁₂-

PV104: -(VAl)₈₁-(HyC22)₁₇-(VAc)₂-

PV105: -(VAl)₆₈-(HyC23)₂₀-(VAc)₁₂-

PV106: -(VAl)₇₀-(HyC23)₁₅-(VAc)₁₈-

PV107: -(VAl)₇₄-(HyC24)₂₀-(VAc)₆-

PV108: -(VAl)₆₃-(HyC24)₂₅-(VAc)₁₂-

PV109: -(VAl)₇₀-(HyC24)₁₀-(VAc)₂₀-

PV110: -(VAl)₈₃-(HyC25)₅-(VAc)₁₂-

PV111: -(VAl)₈₅-(HyC25)₃-(VAc)₁₂-

PV112: -(VAl)₉₀-(HyC25)₈-(VAc)₂-

PV113: -(VAl)₇₈-(HyC26)₁₀-(VAc)₁₂-

PV114: -(VAl)₈₅-(HyC26)₁₃-(VAc)₂-

PV115: -(VAl)₆₇-(HyC26)₂₁-(VAc)₁₂-

PV116: -(VAl)₇₂-(HyC27)16-(VAc)₁₂-

PV117: -(VAl)₈₁-(HyC27)₁₃-(VAc)₆-

PV118: -(VAl)₇₇-(HyC27)₂₁-(VAc)₂-

PV119: -(VAl)₇₀-(HyC28)₂₂-(VAc)₈-

PV120: -(VAl)₆₇-(HyC28)₁₁-(VAc)₁₂-

PV121: -(VAl)₇₀-(HyC28)₂₈-(VAc)₂-

PV122: -(VAl)₆₃-(HyC29)₃₅-(VAc)₂-

PV123: -(VAl)₆₈-(HyC29)₂₄-(VAc)₈-

PV124: -(VAl)₇₆-(HyC29)₁₂-(VAc)₁₂-

PV125: -(VAl)₇₆-(HyC30)₁₂-(VAc)₁₂-S-n-C₁₂H₂₅

PV126: -(VAl)₇₃-(HyC30)₁₅-(VAc)₁₂-S-n-C₁₂H₂₅

PV127: -(VAl)₈₁-(HyC30)₇-(VAc)₁₂-S-n-C₁₂H₂₅

PV128: -(VAl)₇₅-(HyC31)₁₉-(VAc)₆-

PV129: -(VAl)₇₅-(HyC31)₂₃-(VAc)₂-

PV130: -(VAl)₈₀-(HyC31)₁₈-(VAc)₂-

PV131: -(VAl)₆₈-(HyC32)₂₄-(VAc)₈-

PV132: -(VAl)₅₅-(HyC32)₃₃-(VAc)₁₂-

PV133: -(VAl)₆₈-(HyC32)₂₀-(VAc)₁₂-

PV134: -(VAl)₆₈-(HyC33)₂₀-(VAc)₁₂-

PV135: -(VAl)₇₃-(HyC33)₁₅-(VAc)₁₂-

PV136: -(VAl)₇₈-(HyC33)₁₀-(VAc)₁₂-

PV137: -(VAl)₅₃-(HyC34)₃₅-(VAc)₁₂-

PV138: -(VAl)₆₄-(HyC34)₃₀-(VAc)₆-

PV139: -(VAl)₇₃-(HyC34)₂₅-(VAc)₂-

PV140: -(VAl)₇₄-(HyC35)₁₄-(VAc)₁₂-

PV141: -(VAl)₃₈-(HyC35)₅₀-(VAc)₁₂-

PV142: -(VAl)₂₇-(HyC35)₆₅-(VAc)₈-

PV143: -(VAl)₇₂-(HyC36)₂₆-(VAc)₂-

PV144: -(VAl)₆₁-(HyC36)₃₁-(VAc)₈-

PV145: -(VAl)₇₂-(HyC36)₁₆-(VAc)₁₂-

PV146: -(VAl)₅₅-(HyC37)₃₃-(VAc)₁₂-

PV147: -(VAl)₃₂-(HyC37)₅₆-(VAc)₁₂-

PV148: -(VAl)₂₈-(HyC37)₇₀-(VAc)₈-

PV149: -(VAl)₆₃-(HyC38)₂₅-(VAc)₁₂-

PV150: -(VAl)₇₄-(HyC38)₂₀-(VAc)₆-

PV151: -(VAl)₈₃-(HyC38)₁₅-(VAc)₂-

PV152: -(VAl)₆₅-(HyC39)₃₁-(VAc)₂-S-n-C₁₂H₂₅

PV153: -(VAl)₅₁-(HyC39)₄₇-(VAc)₂-S-n-C₁₂H₂₅

PV154: -(VAl)₇₂-(HyC39)₂₀-(VAc)₈-S-n-C₁₂H₂₅

The denatured polyvinyl alcohol containing fluorine atoms comprisesrepeating units containing fluorine atoms preferably in an amount of0.05 to 80 mol %, and more preferably in an amount of 0.5 to 70 mol %.

A preferred denatured polyvinyl alcohol containing fluorine atoms isrepresented by the formula (PVf):

-(VAl)_(x)-(FRU)_(y)-(VAc)_(z)-  (PVf)

in which VAl is a vinyl alcohol repeating unit; FRU is a repeating unitcontaining fluorine atoms; VAc is a vinyl acetate repeating unit; x is20 to 99 mol % (preferably 24 to 98 mol %); y is 0.05 to 80 mol %(preferably 0.5 to 70 mol %); and z is 0 to 30 mol % (preferably 2 to 20mol %).

Preferred repeating units containing fluorine atoms (FRU) arerepresented by the formulas (FRU-I) and (FRU-II):

in which L¹ is a divalent linking group selected from the groupconsisting of —O—, —CO—, —SO₂—, —NH—, -alkylene-, -arylene- and acombination thereof; L² is a single bond or a divalent linking groupselected from the group consisting of —O—, —CO—, —SO₂—, —NH—,-alkylene-, -arylene- and a combination thereof; and each of Rf¹ and Rf²is a hydrocarbon group substituted with fluorine atom.

The alkylene group and the arylene group can be substituted withfluorine atom.

Examples of the divalent linking groups formed by the combinations arethe same as the examples described in the formulas (HyC-I) and (HyC-II).

The hydrocarbon moiety contained in the hydrocarbon group substitutedwith fluorine atom is an aliphatic group, an aromatic group or acombination thereof. The aliphatic group can have a branched or cyclicstructure. The aliphatic group preferably is an alkyl group (including acycloalkyl group) or an alkenyl group (including a cycloalkenyl group).The hydrocarbon group can have a substituent group that is not stronglyhydrophilic, such as a halogen atom (other than fluorine atom). Thehydrocarbon group contains 1 to 100 carbon atoms, preferably 2 to 60carbon atoms, and more preferably 3 to 40 carbon atoms. The substitutionratio of hydrogen atoms in the hydrocarbon group substituted withfluorine atoms is preferably in the range of 50 to 100 mol %, morepreferably in the range of 70 to 100 mol %, further preferably in therange of 80 to 100 mol %, and most preferably in the range of 90 to 100mol %.

Examples of the repeating units containing fluorine atoms are shownbelow.

A specific group other than the repeating units containing fluorineatoms can be attached to the end of the denatured polyvinyl alcohol.Examples of the end groups include an alkylthio group.

Examples of the denatured polyvinyl alcohol containing fluorine atomsare shown below. The ratio of the repeating unit means mol %.

PV201: -(VAl)₈₀-(FRU1)₈-(VAc)₁₂-

PV202: -(VAl)₆₉-(FRU1)₁₉-(VAc)₁₂-

PV203: -(VAl)₇₀-(FRU1)₁₀-(VAc)₂₀-

PV204: -(VAl)₇₄-(FRU2)₂₀-(VAc)₆-

PV205: -(VAl)₆₅-(FRU2)₂₇-(VAc)₁₂-

PV206: -(VAl)₇₀-(FRU2)₁₀-(VAc)₂₀-

PV207: -(VAl)₇₈-(FRU3)i0-(VAc)₁₂-S-n-C₁₂H₂₅

PV208: -(VAl)₈₅-(FRU3)₁₃-(VAc)₂-S-n-C₁₂H₂₅

PV209: -(VAl)₆₇-(FRU3)₂₁-(VAc)₁₂-S-n-C₁₂H₂₅

PV210: -(VAl)₅₈-(FRU4)₄₀-(VAc)₂-

PV211: -(VAl)₄₀-(FRU4)₅₄-(VAc)₆-

PV212: -(VAl)₂₄-(FRU4)₆₄-(VAc)₁₂-

PV213: -(VAl)₅₀-(FRU5)₃₈-(VAc)₁₂-

PV214: -(VAl)₅₃-(FRU5)₄₅-(VAc)₂-

PV215: -(VAl)₃₁-(FRU5)₆₁-(VAc)₈-

PV216: -(VAl)₈₀-(FRU6)₈-(VAc)₁₂-

PV217: -(VAl)₇₆-(FRU6)₁₂-(VAc)₁₂-

PV218: -(VAl)₈₁-(FRU6)₁₅-(VAc)₄-

PV219: -(VAl)₅₅-(FRU7)₄₄-(VAc)₁-

PV220: -(VAl)₄₂-(FRU7)₅₆-(VAc)₂-

PV221: -(VAl)₂₇-(FRU7)₆₁-(VAc)₁₂-

PV222: -(VAl)₄₀-(FRU8)₄₈-(VAc)₁₂-

PV223: -(VAl)₃₃-(FRU8)₅₉-(VAc)₈-

PV224: -(VAl)₂₈-(FRU8)₇₀-(VAc)₂-

PV225: -(VAl)₆₈-(FRU9)₂₀-(VAc)₁₂-

PV226: -(VAl)₆₅-(FRU9)₁₅-(VAc)₂₀-

PV227: -(VAl)₆₄-(FRU9)₂₈-(VAc)₈-

PV228: -(VAl)₇₈-(FRU10)₂₁-(VAc)₁-S-n-C₁₂H₂₅

PV229: -(VAl)₆₆-(FRU10)₃₀-(VAc)₄-S-n-C₁₂H₂₅

PV230: -(VAl)₅₃-(FRU10)₃₅-(VAc)₁₂-S-n-C₁₂H₂₅

PV231: -(VAl)₆₃-(FRU11)₂₅-(VAc)₁₂-

PV232: -(VAl)₈₀-(FRU11)₁₈-(VAc)₂-

PV233: -(VAl)₄₆-(FRU11)₃₄-(VAc)₂₀-

PV234: -(VAl)₆₀-(FRU12)₂₈-(VAc)₁₂-

PV235: -(VAl)₅₃-(FRU12)₃₅-(VAc)₁₂-

PV236: -(VAl)₅₂-(FRU12)₄₀-(VAc)₈-

PV237: -(VAl)₈₈-(FRU13)₁₀-(VAc)₂-

PV238: -(VAl)₆₇-(FRU13)₂₁-(VAc)₁₂-

PV239: -(VAl)₆₂-(FRU13)₃₀-(VAc)₈-

PV240: -(VAl)₈₁-(FRU14)18-(VAc)₁-

PV241: -(VAl)₇₃-(FRU14)₂₅-(VAc)₂-

PV242: -(VAl)₅₈-(FRU14)₃₀-(VAc)₁₂-

PV243: -(VAl)₇₄-(FRU15)₂₅-(VAc)₁-

PV244: -(VAl)₆₈-(FRU15)₃₀-(VAc)₂-

PV245: -(VAl)₅₂-(FRU15)₄₀-(VAc)₈-

PV246: -(VAl)₆₃-(FRU16)₃₅-(VAc)₂-

PV247: -(VAl)₅₅-(FRU16)₄₁-(VAc)₄-

PV248: -(VAl)₃₃-(FRU16)₅₅-(VAc)₁₂-

PV249: -(VAl)₅₃-(FRU17)₃₅-(VAc)₁₂-S-n-C₁₂H₂₅

PV250: -(VAl)₄₀-(FRU17)₄₀-(VAc)₂₀-S-n-C₁₂H₂₅

PV251: -(VAl)₄₈-(FRU17)₄₈-(VAc)₄-S-n-C₁₂H₂₅

PV252: -(VAl)₇₄-(FRU18)₂₅-(VAc)₁-

PV253: -(VAl)₆₁-(FRU18)₃₁-(VAc)₈-

PV254: -(VAl)₄₈-(FRU18)₄₀-(VAc)₁₂-

PV255: -(VAl)₈₆-(FRU19)₁₂-(VAc)₂-

PV256: -(VAl)₇₈-(FRU19)₁₈-(VAc)₄-

PV257: -(VAl)₆₈-(FRU19)₂₄-(VAc)₈-

PV258: -(VAl)₇₆-(FRU20)₂₂-(VAc)₂-

PV259: -(VAl)₅₈-(FRU20)₃₀-(VAc)₁₂-

PV260: -(VAl)₅₀-(FRU20)₃₅-(VAc)₁₅-

PV261: -(VAl)₇₈-(FRU21)₁₀-(VAc)₁₂-

PV262: -(VAl)₇₀-(FRU21)₁₈-(VAc)₁₂-

PV263: -(VAl)₅₇-(FRU21)₃₁-(VAc)₁₂-

The denatured polyvinyl alcohol can have a polymerizable group. Apolymer having a polymerizable group is used in combination with adiscotic liquid crystal molecule having a polymerizable group tochemically bind the polymer and the discotic liquid crystal moleculealong an interface between a liquid crystal layer (such as an opticalanisotropic layer) and an orientation layer. The mechanical strength ofa liquid crystal element (such as an optical compensatory sheet) can beimproved by the chemical bond.

The polymerizable group of the denatured polyvinyl alcohol is determineddepending the polymerizable group (Q) of the liquid crystal molecule(described below). The polymerizable group (Q) of the liquid crystalmolecule preferably is an unsaturated polymerizable group (Q1 to Q7), anepoxy group (Q8) or an aziridinyl group (Q9), more preferably is anunsaturated polymerizable group, and most preferably is an ethylenicallyunsaturated group (Q1 to Q6). The polymerizable group of the denaturedpolyvinyl alcohol is also preferably is an unsaturated polymerizablegroup, an aziridinyl group or an epoxy group, more preferably is anunsaturated polymerizable group, and most preferably is an ethylenicallyunsaturated group.

The polymerizable group is preferably not directly attached to the mainchain of the denatured polyvinyl alcohol. In other words, a linkinggroup preferably intervenes between the main chain and the polymerizablegroup. Examples of the linking groups include —O—, —O—CO—, —O—CO—NH—,—O—CO—NH-alkylene-, —O—CO—NH-alkylene-O—, —O—CO—NH-alkylene-CO—O—,—O—CO—NH-alkylene-O—CO—, —O—CO—NH-alkylene-CO—NH—, —O—CO-alkylene-O—CO—,—O—CO-arylene-O-alkylene-O—CO—, —O—CO-arylene-O-alkylene-O—,—O—CO-arylene-O-alkylene- and —O-alkylene-O—CO—, in which the left sideis attached to the main chain, and the right side is attached to thepolymerizable group.

The alkylene group can have a branched or cyclic structure. The alkylenegroup contains preferably 1 to 30 carbon atoms, more preferably 1 to 20carbon atoms, further preferably 1 to 15 carbon atoms, and mostpreferably 1 to 12 carbon atoms.

The arylene group preferably is phenylene or naphthylene, morepreferably is phenylene, and most preferably is p-phenylene. The arylenegroup can have a substituent group. Examples of the substituent groupsinclude a halogen atom (F, Cl, Br), carboxyl, cyano, nitro, carbamoyl,sulfamoyl, an alkyl group, a cycloalkyl group, an alkoxy group, analkylthio group, an acyl group, an acyloxy group, an alkylcarbamoylgroup, an alkylsulfamoyl group, an amido group, a sulfonamido group andan alkylsulfonyl group.

The alkyl group can have a branched structure. The alkyl grouppreferably contains 1 to 20 carbon atoms, more preferably contains 1 to15 carbon atoms, further preferably contains 1 to 10 carbon atoms, andmost preferably contains 1 to 6 carbon atoms.

The cycloalkyl group preferably is cyclohexyl.

The alkoxy group can have a branched structure. The alkoxy grouppreferably contains 1 to 20 carbon atoms, more preferably contains 1 to15 carbon atoms, further preferably contains 1 to 10 carbon atoms, andmost preferably contains 1 to 6 carbon atoms.

The alkylthio group can have a branched structure. The alkylthio grouppreferably contains 1 to 20 carbon atoms, more preferably contains 1 to15 carbon atoms, further preferably contains 1 to 10 carbon atoms, andmost preferably contains 1 to 6 carbon atoms.

The acyl group-preferably contains 2 to 20 carbon atoms, more preferablycontains 2 to 15 carbon atoms, further preferably contains 2 to 10carbon atoms, and most preferably contains 2 to 6 carbon atoms.

The acyloxy group preferably contains 2 to 20 carbon atoms, morepreferably contains 2 to 15 carbon atoms, further preferably contains 2to 10 carbon atoms, and most preferably contains 2 to 6 carbon atoms.

The alkylcarbamoyl group preferably contains 2 to 20 carbon atoms, morepreferably contains 2 to 15 carbon atoms, further preferably contains 2to 10 carbon atoms, and most preferably contains 2 to 6 carbon atoms.The alkyl moiety of the alkylcarbamoyl group can further have asubstituent group (e.g., an alkoxy group).

The alkylsulfamoyl group preferably contains 1 to 20 carbon atoms, morepreferably contains 1 to 15 carbon atoms, further preferably contains 1to 10 carbon atoms, and most preferably contains 1 to 6 carbon atoms.The alkyl moiety of the alkylsulfamoyl group can further have asubstituent group (e.g., an alkoxy group).

The amido group preferably contains 2 to 20 carbon atoms, morepreferably contains 2 to 15 carbon atoms, further preferably contains 2to 10 carbon atoms, and most preferably contains 2 to 6 carbon atoms.

The sulfonamido group preferably contains 1 to 20 carbon atoms, morepreferably contains 1 to 15 carbon atoms, further preferably contains 1to 10 carbon atoms, and most preferably contains 1 to 6 carbon atoms.

The alkylsulfonyl group preferably contains 1 to 20 carbon atoms, morepreferably contains 1 to 15 carbon atoms, further preferably contains 1to 10 carbon atoms, and most preferably contains 1 to 6 carbon atoms.The alkyl moiety of the alkylsulfonyl group can further have asubstituent group (e.g., an alkoxy group).

The denatured polyvinyl alcohol can have two or more polymerizablegroups.

A repeating unit having the polymerizable group is preferablyrepresented by the formula (II).

In the formula (II), L¹¹ is a single bond or a divalent linking groupselected from the group consisting of —CO—, —CO—NH—, —CO—NH-alkylene-,—CO—NH-alkylene-O—, —CO—NH-alkylene-CO—O—, —CO—NH-alkylene-O—CO—,—CO—NH-alkylene-CO—NH—, —CO-alkylene-O—CO—,—CO-arylene-O-alkylene-O—CO—, —CO-arylene-O-alkylene-O—,—CO-arylene-O-alkylene- and -alkylene-O—CO—. L¹¹ preferably is—CO—NH-alkylene-, —CO—NH-alkylene-O—, —CO—NH-alkylene-O—CO—,—CO-arylene-O-alkylene-O—CO—, —CO-arylene-O-alkylene-O—,—CO-arylene-O-alkylene- or -alkylene-O—CO—, and particularly preferablyis —CO—NH-alkylene-O—CO—.

The alkylene group can have a branched or cyclic structure. The alkylenegroup contains preferably 1 to 30 carbon atoms, more preferably 1 to 20carbon atoms, further preferably 1 to 15 carbon atoms, and mostpreferably 1 to 12 carbon atoms.

The arylene group preferably is phenylene or naphthylene, morepreferably is phenylene, and most preferably is p-phenylene. The arylenegroup can have a substituent group. Examples of the substituent groupsare the same as the above-described substituent groups.

In the formula (II), Q is a polymerizable group. The polymerizable groupof the denatured polyvinyl alcohol is analogous to the polymerizablegroup (Q) of the liquid crystal molecule, as is described above.

Examples of the repeating units having a polymerizable group are shownbelow.

The polymerizable group can be introduced into the repeating unit grouphaving a hydrocarbon group containing 10 to 100 carbon atoms or therepeating unit containing fluorine atoms. The polymerizable grouppreferably is a substituent group of a hydrocarbon group or ahydrocarbon group substituted with fluorine atom, and more preferably isa substituent group of the hydrocarbon group (or the hydrocarbon groupsubstituted with fluorine atom) positioned at the end of the side chain.

The polymerizable group is preferably not directly attached to thehydrocarbon group (or the hydrocarbon group substituted with fluorineatom). In other words, a linking group preferably intervenes between thehydrocarbon group and the polymerizable group. Examples of the linkinggroups include —O—, —CO—, —O—CO—, —CO—O—, —O—CO—O—, —CO—NH, —SO₂—NH—,—NH—CO—, —NH—CO—O—, —NH—SO₂—, -alkylene-, -alkenylene-, -alkynylene-,—O-alkylene- and -alkylene-O—, in which the left side is attached to thehydrocarbon group, and the right side is attached to the polymerizablegroup.

The alkylene group can have a branched or cyclic structure. The alkylenegroup contains preferably 1 to 30 carbon atoms, more preferably 1 to 20carbon atoms, further preferably 1 to 15 carbon atoms, and mostpreferably 1 to 12 carbon atoms.

The alkenylene group can have a branched or cyclic structure. Thealkenylene group contains preferably 2 to 30 carbon atoms, morepreferably 2 to 20 carbon atoms, further preferably 2 to 15 carbonatoms, and most preferably 2 to 12 carbon atoms.

The alkynylene-group can have a branched or cyclic structure. Thealkynylene group contains preferably 2 to 30 carbon atoms, morepreferably 2 to 20 carbon atoms, further preferably 2 to 15 carbonatoms, and most preferably 2 to 12 carbon atoms.

The hydrocarbon group (or the hydrocarbon group substituted withfluorine atom) can have two or more polymerizable groups.

A repeating unit having the polymerizable group and the hydrocarbongroup is preferably represented by the formula (III).

In the formula (III), L²¹ is a divalent linking group selected from thegroup consisting of —O—, —CO—, —SO₂—, —NH—, -alkylene-, -arylene- and acombination thereof. L²¹ is the same as L¹ in the formula (HyC-I) or(FRU-I).

In the formula (III), R²¹ is a hydrocarbon group containing 10 to 100carbon atoms or a hydrocarbon group substituted with fluorine atom. Thehydrocarbon group containing 10 to 100 carbon atoms is the same as R¹ inthe formula (HyC-I). The hydrocarbon group containing fluorine atom isthe same as Rf¹ in the formula (FRU-I).

In the formula (III), L²² is a single bond or a divalent linking groupselected from the group consisting of —O—, —CO—, —O—CO—, —CO—O—,—O—CO—C—, —CO—NH, —SO₂—NH—, —NH—CO—, —NH—CO—O—, —NH—SO₂—, -alkylene-,-alkenylene-, -alkynylene-, —O-alkylene- and -alkylene-O—.

The alkylene group, the alkenylene group and the alkylene group are thesame as those described above.

In the formula (III), Q is a polymerizable group. The polymerizablegroup of the denatured polyvinyl alcohol is analogous to thepolymerizable group (Q) of the liquid crystal molecule, as is describedabove.

In the formula (III), p is 1, 2 or 3, preferably is 1 or 2, and morepreferably is 1.

In the case that a repeating unit having a polymerizable group isintroduced into a denatured polyvinyl alcohol, the polyvinyl alcoholpreferably contains the polymerizable repeating units in an amount of0.1 to 10 mol %, and more preferably in an amount of 3 to 50 mol %.

In the case that a repeating unit having a hydrocarbon group (or ahydrocarbon group substituted with fluorine atom) and a polymerizablegroup is introduced into a denatured polyvinyl alcohol, the polyvinylalcohol preferably contains the polymerizable hydrocarbon repeatingunits in an amount of 2 to 80 mol %, and more preferably in an amount of3 to 50 mol %.

A denatured polyvinyl alcohol having (1) a repeating unit having ahydrocarbon group (or a hydrocarbon group substituted with fluorineatom), and (2) a repeating unit having a polymerizable group ispreferably represented by the formula (PVII):

-(VAl)_(x)-(I)_(a)-(II)_(b)-(VAc)_(y)-  (PVII)

in which VAl is a vinyl alcohol repeating unit; I is a repeating unithaving a hydrocarbon group containing 10 to 100 carbon atoms or arepeating unit having a hydrocarbon group substituted with fluorineatom; II is a repeating unit having a polymerizable group; VAc is avinyl acetate repeating unit; x is 20 to 95 mol % (preferably 30 to 95mol %); a is 2 to 80 mol % (preferably 3 to 50 mol %); b is 0.1 to 10mol % (preferably 0.2 to 5 mol %); and y is 0 to 30 mol % (preferably 1to 20 mol %).

A denatured polyvinyl alcohol having (3) a repeating unit having ahydrocarbon group (or a hydrocarbon group substituted with fluorineatom) and a polymerizable group is preferably represented by the formula(PVIII):

-(VAl)_(x)-(III)_(c)-(VAc)_(y)-  (PVIII)

in which VAl is a vinyl alcohol repeating unit; III is a repeating unithaving a polymerizable group and a hydrocarbon group containing 10 to100 carbon atoms or a repeating unit having a polymerizable group and ahydrocarbon group substituted with fluorine atom; VAc is a vinyl acetaterepeating unit; x is 20 to 95 mol % (preferably 30 to 95 mol %); c is 2to 80 mol % (preferably 3 to 50 mol %); and y is 0 to 30 mol %(preferably 1 to 20 mol %)

A denatured polyvinyl alcohol can have a combination of theabove-described repeating units. Accordingly, the present invention canuse a denatured polyvinyl alcohol having the repeating units (1) and(3), a denatured polyvinyl alcohol having the repeating units (2) and(3), or a denatured polyvinyl alcohol having the repeating units (1),(2) and (3).

A hydrophilic group can be introduced into the denatured polyvinylalcohol. In the case that a denatured polyvinyl alcohol has ahydrophilic group, an orientation layer can be formed by using anaqueous medium. Even if polyvinyl alcohol is denatured to some extent,the polyvinyl alcohol has many hydroxyl groups, which are rather stronghydrophilic groups. Therefore, it has been considered that a denaturedpolyvinyl can be dissolved in an aqueous medium. However, the applicantssurprisingly note that the above-described denatured polyvinyl alcoholis sometimes not dissolved in an aqueous medium. The hydrophilic groupis preferably introduced into the denatured polyvinyl alcohol in thecase that the denatured polyvinyl alcohol is not dissolved in an aqueousmedium.

The hydrophilic group has a hydrophilic characteristic stronger thanthat of hydroxyl of polyvinyl alcohol. A repeating unit having thestrongly hydrophilic group is preferably introduced into a denaturedpolyvinyl alcohol. A solubility of a denatured polyvinyl alcohol havingthe strongly hydrophilic repeating units in water is preferably largerthan a solubility of a denatured polyvinyl alcohol having hydroxyl inplace of the strongly hydrophilic repeating units.

Examples of the hydrophilic groups include an anionic hydrophilic group,a cationic hydrophilic group and a nonionic hydrophilic group. Examplesof the cationic groups include carboxyl and sulfo. An alcoholate and aphenolate can also be used as the anionic group. Examples of thecationic group include ammonium groups. Amino, an amido group, asulfonamido group, hydrazino, hydrazido, carbamoyl and sulfamoyl canalso be used as the anionic group. The anionic group or the cationicgroup is preferably in the form of a salt. The counter ion of theanionic group preferably is an alkali metal ion or an ammonium ion. Thecounter ion of the cationic group preferably is a halide ion. Examplesof the nonionic group (having a hydrophilic characteristic stronger thanthat of hydroxyl) include a group comprising polyethylene glycol units.

Examples of the hydrophilic groups are shown below.

The hydrophilic group is preferably not directly attached to the mainchain of the denatured polyvinyl alcohol. In other words, a linkinggroup preferably intervenes between the main chain and the hydrophilicgroup. Examples of the linking groups include —O—, —O—CO—, —O—CO—NH—,—O—CO—NH-alkylene-, —O—CO—NH-alkylene-O—, —O—CO—NH-alkylene-CO—O—,—O—CO—NH-alkylene-O—CO—, —O—CO—NH-alkylene-CO—NH—, —O—CO—NH-arylene-,—O—CO-alkylene-, —O—CO-alkenylene-, —O—CO-arylene-,—O—CO-alkylene-O—CO—, —O—CO-arylene-O-alkyene-O—CO—,—O—CO-arylene-O-alkylene-O—, —O—CO-arylene-O-alkylene-, —O-alkylene- and—O-alkylene-O—CO—, in which the left side is attached to the main chain,and the right side is attached to the hydrophilic group.

The alkylene group can have a branched or cyclic structure. The alkylenegroup contains preferably 1 to 30 carbon atoms, more preferably 1 to 20carbon atoms, further preferably 1 to 15 carbon atoms, and mostpreferably 1 to 12 carbon atoms.

The alkenylene group can have a branched or cyclic structure. Thealkenylene group contains preferably 2 to 30 carbon atoms, morepreferably 2 to 20 carbon atoms, further preferably 2 to 15 carbonatoms, and most preferably 2 to 12 carbon atoms.

The arylene group preferably is phenylene or naphthylene, morepreferably is phenylene, and most preferably is p-phenylene. The arylenegroup can have a substituent group. Examples of the substituent groupsare the same as those described about the polymerizable group.

The denatured polyvinyl alcohol can have two or more hydrophilic groups.The denatured polyvinyl alcohol can have two or more kinds ofhydrophilic groups (namely an amphoteric hydrophilic group).

A repeating unit having the hydrophilic group is preferably representedby the formula (IV).

In the formula (IV), L³¹ is a single bond or a divalent linking groupselected from the group consisting of —CO—, —CO—NH—, —CO—NH-alkylene-,—CO—NH-alkylene-O—, —CO—NH-alkylene-CO—O—, —CO—NH-alkylene-O—CO—,—CO—NH-alkylene-CO—NH—, —CO—NH-arylene-, —CO-alkylene-, —CO-alkenylene-,—CO-arylene-, —CO-alkylene-O—CO—, —CO-arylene-O-alkylene-O-CO—,—CO-arylene-O-alkylene-o—, —CO-arylene-O-alkylene-, -alkylene- and-alkylene-O—CO—.

The alkylene group can have a branched or cyclic structure. The alkylenegroup contains preferably 1 to 30 carbon atoms, more preferably 1 to 20carbon atoms, further preferably 1 to 15 carbon atoms, and mostpreferably 1 to 12 carbon atoms.

The alkenylene group can have a branched or cyclic structure. Thealkenylene group contains preferably 2 to 30 carbon atoms, morepreferably 2 to 20 carbon atoms, further preferably 2 to 15 carbonatoms, and most preferably 2 to 12 carbon atoms.

The arylene group preferably is phenylene or naphthylene, morepreferably is phenylene, and most preferably is p-phenylene. The arylenegroup can have a substituent group. Examples of the substituent groupsare the same as those described about the polymerizable group.

In the formula (IV), Hy is a hydrophilic group, which has a hydrophiliccharacteristic stronger than that of hydroxyl in polyvinyl alcohol. Theexamples of the hydrophilic groups are described above.

Examples of the repeating units having a hydrophilic group are shownbelow.

The hydrophilic group can be introduced into the repeating unit grouphaving a hydrocarbon group containing 10 to 100 carbon atoms or therepeating unit containing fluorine atoms. The hydrophilic grouppreferably is a substituent group of a hydrocarbon group or ahydrocarbon group substituted with fluorine atom, and more preferably isa substituent group of the hydrocarbon group (or the hydrocarbon groupsubstituted with fluorine atom) placed at the nearest position to themain chain.

A linking group can intervene between the hydrocarbon group and thehydrophilic group. Examples of the linking groups include —O—, —CO—,—O—CO—, —CO—O—, —O—CO—O—, —CO—NH, —SO₂—NH—, —NH—CO—, —NH—CO—O—,—NH—SO₂—, -alkylene-, -alkenylene-, -alkynylene-, —O-alkylene- and-alkylene-O—, in which the left side is attached to the hydrocarbongroup, and the right side is attached to the hydrophilic group.

The alkylene group can have a branched or cyclic structure. The alkylenegroup contains preferably 1 to 30 carbon atoms, more preferably 1 to 20carbon atoms, further preferably 1 to 15 carbon atoms, and mostpreferably 1 to 12 carbon atoms.

The alkenylene group can have a branched or cyclic structure. Thealkenylene group contains preferably 2 to 30 carbon atoms, morepreferably 2 to 20 carbon atoms, further preferably 2 to 15 carbonatoms, and most preferably 2 to 12 carbon atoms.

The alkynylene group can have a branched or cyclic structure. Thealkynylene group contains preferably 2 to 30 carbon atoms, morepreferably 2 to 20 carbon atoms, further preferably 2 to 15 carbonatoms, and most preferably 2 to 12 carbon atoms.

The hydrocarbon group (or the hydrocarbon group substituted withfluorine atom) can have two or more hydrophilic groups.

A repeating unit having the hydrophilic group and the hydrocarbon groupis preferably represented by the formula (V).

In the formula (V), L⁴¹ is a divalent linking group selected from thegroup consisting of —O—, —CO—, —SO₂—, —NH—, -alkylene-, -arylene- and acombination thereof. L⁴¹ is the same as L¹ in the formula (HyC-I) or(FRU-I).

In the formula (V), R⁴¹ is a hydrocarbon group containing 10 to 100carbon atoms or a hydrocarbon group substituted with fluorine atom. Thehydrocarbon group containing 10 to 100 carbon atoms is the same as R¹ inthe formula (HyC-I). The hydrocarbon group containing fluorine atom isthe same as Rf¹ in the formula (FRU-I).

In the formula (V), L⁴² is a single bond or a divalent linking groupselected from the group consisting of —O—, —CO—, —O—CO—, —CO—O—,—O—CO—O—, —CO—NH—, —SO₂—NH—, —NH—CO—, —NH—CO—O—, —NH—SO₂—, -alkylene-,-alkenylene-, -alkynylene, —O-alkylene- and -alkylene-O—.

The alkylene group, the alkenylene group and the alkylene group are thesame as those described above.

In the formula (V), Hy is a hydrophilic group. The hydrophilic groupsare the same as those described above.

In the formula (V), p is 1, 2 or 3, preferably is 1 or 2, and morepreferably is 1.

In the case that a repeating unit having a hydrophilic group isintroduced into a denatured polyvinyl alcohol, the polyvinyl alcoholpreferably contains the hydrophilic repeating units in an amount of 3 to90 mol %, and more preferably in an amount of 4 to 70 mol %.

In the case that a repeating unit having a hydrocarbon group (or ahydrocarbon group substituted with fluorine atom) and a hydrophilicgroup is introduced into a denatured polyvinyl alcohol, the polyvinylalcohol preferably contains the hydrophilic hydrocarbon repeating unitsin an amount of 2 to 80 mol %, and more preferably in an amount of 3 to50 mol %.

A denatured polyvinyl alcohol having (1) a repeating unit having ahydrocarbon group (or a hydrocarbon group substituted with fluorineatom), and (4) a repeating unit having a hydrophilic group is preferablyrepresented by the formula (PVIV):

-(VAl)_(x)-(I)_(a)-(IV)_(d)-(VAc)_(y)-  (PVIV)

in which VAl is a vinyl alcohol repeating unit; I is a repeating unithaving a hydrocarbon group containing 10 to 100 carbon atoms or arepeating unit having a hydrocarbon group substituted with fluorineatom; IV is a repeating unit having a hydrophilic group; VAc is a vinylacetate repeating unit; x is 20 to 95 mol % (preferably 30 to 95 mol %);a is 2 to 80 mol % (preferably 3 to 50 mol %); d is 3 to 90 mol %(preferably 4 to 70 mol %); and y is 0 to 30 mol % (preferably 1 to 20mol %).

A denatured polyvinyl alcohol having (5) a repeating unit having ahydrocarbon group (or a hydrocarbon group substituted with fluorineatom) and a hydrophilic group is preferably represented by the formula(PVV):

-(VAl)_(x)-(V)_(e)-(VAc)_(y)-  (PVW)

in which VAl is a vinyl alcohol repeating unit; V is a repeating unithaving a hydrophilic group and a hydrocarbon group containing 10 to 100carbon atoms or a repeating unit having a hydrophilic group and ahydrocarbon group substituted with fluorine atom; VAc is a vinyl acetaterepeating unit; x is 20 to 95 mol % (preferably 30 to 95 mol %); e is 2to 80 mol % (preferably 3 to 50 mol %); and y is 0 to 30 mol %(preferably 1 to 20 mol %).

A denatured polyvinyl alcohol can have a combination of theabove-described repeating units. Accordingly, the present invention canuse a denatured polyvinyl alcohol having the repeating units (1) and(5), a denatured polyvinyl alcohol having the repeating units (4) and(5), or a denatured polyvinyl alcohol having the repeating units (1),(4) and (5).

The denatured polyvinyl alcohol can be prepared according to aconventional method. For example, polyvinyl alcohol can be denatured byreacting hydroxyl (—OH) of polyvinyl alcohol with a carbonyl acidcorresponding to an additional side chain (HOOC-side chain) to form anadditional repeating unit having an ester bond (main chain-O—CO-sidechain). Polyvinyl alcohol can also be denatured by reacting hydroxylwith an aldehyde corresponding to a side chain to form an additionalrepeating unit having an acetal bond. The other denatured polyvinylalcohol can also be prepared in a similar manner.

The denatured polyvinyl alcohol has a polymerization degree preferablyin the range of 200 to 5,000, and more preferably in the range of 300 to3,000. The denatured polyvinyl alcohol has a molecular weight preferablyin the range of 9,000 to 200,000, and more preferably in the range of13,000 to 130,000.

Two or more denatured polyvinyl alcohols can be used in combination.

The denatured polyvinyl alcohol can have a cross-linked structure. Across-linking reaction is preferably conducted simultaneously with orafter coating a solution of the orientation layer on a substrate.

The denatured polyvinyl alcohol can be cross-linked by using across-linking agent. Examples of the cross-linking agents include analdehyde, a dioxane (e.g., 2,3-dihydroxydioxane), a carbenium,2-naphthalate sulfonate, 1,1-bispyrrolidino-1-Chloropyridinium,1-morphorinocarbonyl-3-sulfonatoaminomethyl, an active vinyl compound(e.g., 1,3,5-triacryloyl-hexahydro-s-triazine, bis(vinylsulfone)methane,N,N′-methylenebis-[β-(vinylsulfonyl)propionamide], an active halogencompound (e.g., 2,4-dichloro-6-hydroxy-S-triazine) and an isooxazole. Analdehyde (e.g., formaldehyde, glyoxal, glutaraldehyde, malonaldehyde,phthalaldehyde, terephthalaldehyde, succinaldehyde, isophthalaldehyde,dialdehyde starch) is preferred, an aldehyde having two or morefunctional groups is more preferred, and an aldehyde having twofunctional groups is most preferred.

An acetal reaction is caused between the aldehyde and hydroxyl of adenatured polyvinyl alcohol to cross-link the denatured polyvinylalcohol. A cross-linked repeating unit obtained by an aldehyde havingtwo functional groups (two aldehydo groups) is shown in the followingformula (VI):

in which L⁵¹ is a divalent linking group, which bound the two aldehydogroups in the aldehyde.

The acetal reaction of aldehyde and hydroxyl proceeds in an acidiccondition. An inorganic acid (e.g., sulfuric acid, hydrochloric acid,nitric acid, phosphoric acid) or an organic acid (e.g., dichloroaceticacid, trifluoroacetic acid, methanesulfonic acid, p-toluenesulfonicacid, benzenesulfonic acid, monochloroacetic acid) is preferably addedto a coating solution of an orientation layer to obtain an acidicreaction condition.

The coating amount of the cross-linking agent is preferably in the rangeof 0.1 to 20 wt. %, and more preferably in the range of 0.5 to 15 wt. %,based on the total coating amount of the orientation layer. The amountof the remaining (not reacted) cross-linking agent is preferably notmore than 1.0 wt. %, and more preferably not more than 0.5 wt. %, basedon the coating amount of the orientation layer.

The orientation layer has a thickness preferably in the range of 0.1 to10 μm.

The orientation layer is preferably formed by rubbing the polymer. Therubbing treatment can be conducted by rubbing a layer containing thedenatured polyvinyl alcohol with a paper or cloth several times along acertain direction.

After aligning liquid crystal molecules by the orientation layer, thealignment of the liquid crystal molecules can be kept without theorientation layer. For examples, an aligned optically anisotropic layer(without the orientation layer) can be transferred on a transparentsubstrate to prepare an optical compensatory sheet.

[Liquid Crystal Layer]

The liquid crystal molecules are contained in a liquid crystal layer tobe aligned by using the above-described orientation layer. Theorientation layer has a function of aligning the liquid crystal moleculeessentially vertically (at an average inclined angle in the range of 500to 900).

The liquid crystal molecule preferably is a rod-like liquid crystalmolecule or a discotic liquid crystal molecule. The inclined angle ofthe rod-like liquid crystal molecule means an angle between a long axisof a rod-like liquid crystal molecule and a surface of a substrate (or asurface of an-orientation layer). The inclined angle of the discoticliquid crystal molecule means an angle between a discotic plane of adiscotic liquid crystal molecule and a surface of a substrate (or asurface of an orientation layer).

In the case that a liquid crystal element is used as a liquid crystalcell, rod-like liquid crystal molecules are preferably used.

Examples of the rod-like liquid crystal molecules include azomethines,azoxys, cyanobiphenyls, cyanophenyl esters, benzoic esters, phenylcyclohexanecarboxylates, cyanophenylcyclohexanes, cyanophenylpyridines,alkoxylphenylpyridines, alkoxyphenylpyrimidines, phenyldioxanes, tolanesand alkenylcyclohexylbenzonitriles.

A representative liquid crystal cell containing vertically alignedrod-like liquid crystal molecules is a liquid crystal cell of avertically aligned (VA) mode. A liquid crystal display having the cellof the VA mode is described in Nikkei Microdevice No. 136, page 147(written in Japanese, 1996), Japanese Patent Provisional Publication No.2(1990)-176625 and Japanese Patent No. 2,866,372.

[Optically Anisotropic Layer]

In the case that the liquid crystal element is used as an opticalcompensatory sheet, the liquid crystal layer functions as an opticalanisotropic layer. The optically anisotropic layer preferably comprisesrod-like liquid crystal molecules or discotic liquid crystal molecules,and more preferably comprises discotic liquid crystal molecules.

In the optically anisotropic layer, discotic planes of discotic liquidcrystal molecules are aligned essentially vertically to the orientationlayer (at an average inclined angle in the range of 50° to 90°). Thediscotic liquid crystal molecules are preferably fixed in the opticalanisotropic layer while keeping the vertical (homogeneous) alignment.The discotic liquid crystal molecules are preferably fixed by apolymerization reaction.

The discotic liquid crystal molecule is described in various documents(C. Destrade et al, Mol. Crysr. Liq. Cryst., vol. 71, page 111 (1981);Japan Chemical Society, Quarterly Chemical Review (written in Japanese),chapter 5 and chapter 10, section 2 (1994); B. Kohne et al., Angew.Chem. Soc. Chem. Comm., page 1794 (1985); and J. Zhang et al., J. Am.Chem. Soc., vol. 116, page 2655 (1994)). The polymerization reaction ofthe discotic liquid crystal molecule is described in Japanese PatentProvisional Publication No. 8(1996)-27284.

A polymerizable group should be bound to a discotic core of the discoticliquid crystal molecule to cause the polymerization reaction of thecompound. However, if the polymerizable group is directly bound to thediscotic core, it is difficult to keep the alignment at thepolymerization reaction. Therefore, a linking group is introducedbetween the discotic core and the polymerizable group. Accordingly, thediscotic liquid crystal molecule having a polymerizable group(polymerizable discotic liquid crystal molecule) preferably is acompound represented by the following formula.

D(—L—Q)_(n)

in which D is a discotic core; L is a divalent linking group; Q is apolymerizable group; and n is an integer of 4 to 12.

Examples of the discotic cores (D) are shown below. In the examples, LQ(or QL) means the combination of the divalent linking group (L) and thepolymerizable group (Q).

In the formula, the divalent linking group (L) preferably is selectedfrom the group consisting of an alkylene group, an alkenylene group, anarylene group, —CO, —NH—, —O—, —S— and combinations thereof. L morepreferably is a divalent linking group comprising at least two divalentgroups selected from the group consisting of an alkylene group, anarylene group, —CO—, —NH—, —O— and —S—. L more preferably is a divalentlinking group comprising at least two divalent groups selected from thegroup consisting of an alkylene group, an arylene group, —CO— and —O—.The alkylene group preferably has 1 to 12 carbon atoms. The alkenylenegroup preferably has 2 to 12 carbon atoms. The arylene group preferablyhas 6 to 10 carbon atoms. The alkylene group, the alkenylene group andthe arylene group can have a substituent group (such as an alkyl group,a halogen atom, cyano, an alkoxy group, an acyloxy group).

Examples of the divalent linking groups (L) are shown below. In theexamples, the left side is attached to the discotic core (D), and theright side is attached to the polymerizable group (Q). The AL means analkylene group or an alkenylene group. The AR means an arylene group.

L1: —AL—CO—O—AL—O—CO—

L2: —AL—CO—O—AL—O—

L3: —AL—CO—O—AL—O—AL—

L4: —AL—CO—O—AL—O—CO—

L5: —CO—AR—O—AL—

L6: —CO—AR—O—AL—O—

L7: —CO—AR—O—AL—O—CO—

L8: —CO—NH—AL

L9: —NH—AL—O—

L10: —NH—AL—O—CO—

L11: —O—AL—

L12: —O—AL—O—

L13: —O—AL—O—CO—

L14: —O—AL—O—CO—NH—AL—

L15: —O—AL—S—AL—

L16: —O—CO—AL—AR—O—AL—O—CO—

L17: —O—CO—AR—O—AL—CO—

L18: —O—CO—AR—O—AL—O—CO—

L19: —O—CO—AR—O—AL—O—AL—O—CO—

L20: —O—CO—AR—O—AL—O—AL—O—AL—O—CO—

L21: —S—AL—

L22: —S—AL—O—

L23: —S—AL—O—CO—

L24: —S—AL—S—AL—

L25: —S—AR—AL—

The discotic liquid crystal molecules can be spirally twisted byintroducing asymmetric carbon atom into the molecules, preferably intoAL (an alkylene group or an alkenylene group) of the divalent linkinggroup (L). Examples of AL* containing asymmetric carbon atoms are shownbelow. In the examples, the left side is adjacent to the discotic core(D), and the right side is adjacent to the polymerizable group (Q). Thecarbon atom (C) with the mark (*) is the asymmetric carbon atom. Theoptical activity can be S or R.

AL*1: —CH₂CH₂—C*HCH₃—CH₂CH₂CH₂—

AL*2: —CH₂CH₂CH₂—C*HCH₃—CH₂CH₂—

AL*3: —CH₂—C*HCH₃—CH₂CH₂CH₂CH₂—

AL*4: —C*HCH₃—CH₂CH₂CH₂CH₂CH₂—

AL*5: —CH₂CH₂CH₂CH₂—C*HCH₃—CH₂—

AL*6: —CH₂CH₂CH₂CH₂CH₂—C*HCH₃—

AL*7: —C*HCH₃—CH₂CH₂CH₂CH₂—

AL*8: —CH₂—C*HCH₃—CH₂CH₂CH₂—

AL*9: —CH₂CH₂—C*HCH₃—CH₂CH₂—

AL*10: —CH₂CH₂CH₂—C*HCH₃—CH₂—

AL*11: —CH₂CH₂CH₂CH₂—C*HCH₃—

AL*12: —C*HCH₃—CH₂CH₂CH₂—

AL*13: —CH₂—C*HCH₃—CH₂CH₂—

AL*14: —CH₂CH₂—C*HCH₃—CH₂—

AL*15: —CH₂CH₂CH₂—C*HCH₃—

AL*16: —CH₂—C*HCH₃—

AL*17: —C*HCH₃—CH₂—

AL*18: —C*HCH₃—CH₂CH₂CH₂CH₂CH₂CH₂—

AL*19: —CH₂—C*HCH₃—CH₂CH₂CH₂CH₂CH₂—

AL*20: —CH₂CH₂—C*HCH₃—CH₂CH₂CH₂CH₂—

AL*21: —CH₂CH₂CH₂—C*HCH₃—CH₂CH₂CH₂—

AL*22: —C*HCH₃—CH₂CH₂CH₂CH₂CH₂CH₂CH₂—

AL*23: —CH₂—C*HCH₃—CH₂CH₂CH₂CH₂CH₂CH₂—

AL*24: —CH₂CH₂—C*HCH₃—CH₂CH₂CH₂CH₂CH₂—

AL*25: —CH₂CH₂CH₂—C*HCH₃—CH₂CH₂CH₂CH₂—

AL*26: —C*HCH₃—CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—

AL*27: —CH₂—C*HCH₃—CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—

AL*28: —CH₂—C*HCH₂CH₃—

AL*29: —CH₂—C*HCH₂CH₃—CH₂—

AL*30: —CH₂—C*HCH₂CH₃—CH₂CH₂—

AL*31: —CH₂—C*HCH₂CH₃—CH₂CH₂CH₂CH₂—

AL*32: —CH₂—C*H(n—C₃H₇)—CH₂CH₂—

AL*33: —CH₂—C*H(n—C₃H₇)—CH₂CH₂CH₂CH₂—

AL*34: —CH₂—C*H(OCOCH₃)—CH₂CH₂—

AL*35: —CH₂—C*H(OCOCH₃)—CH₂CH₂CH₂CH₂—

AL*36: —CH₂—C*HF—CH₂CH₂—

AL*37: —CH₂—C*HF—CH₂CH₂CH₂CH₂—

AL*38: —CH₂—C*HClCH₂CH₂—

AL*39: —CH₂—C*HCl—CH₂CH₂CH₂CH₂—

AL*40: —CH₂—C*HOCH₃—CH₂CH₂—

AL*41: —CH₂—C*HOCH₃—CH₂CH₂CH₂CH₂—

AL*42: —CH₂—C*HCN—CH₂CH₂—

AL*43: —CH₂—C*HCN—CH₂CH₂CH₂CH₂—

AL*44: —CH₂—C*HCF₃—CH₂CH₂—

AL*45: —CH₂—C*HCF₃—CH₂CH₂CH₂CH₂—

The polymerizable group (Q) is determined by the polymerizationreaction. Examples of the polymerizable groups (Q) are shown below.

The polymerizable group (Q) preferably is an unsaturated polymerizablegroup (Q1 to Q7), an epoxy group (Q8) or an aziridinyl group (Q9), morepreferably is an unsaturated polymerizable group, and most preferably isan ethylenically unsaturated group (Q1 to Q6).

In the formula, n is an integer of 4 to 12, which is determined by thechemical structure of the discotic core (D). The 4 to 12 combinations ofL and Q can be different from each other. However, the combinations arepreferably identical.

Two or more discotic liquid crystal molecules can be used incombination. For example, a molecule containing asymmetric carbon atomin the divalent linking group (L) can be used in combination with amolecule containing no asymmetric carbon atom. Further, a moleculehaving a polymerizable group (Q) can be used in combination with amolecule having no polymerizable group. A molecule containing asymmetriccarbon atom and having no polymerizable group is preferably used incombination with a molecule having a polymerizable group and containingno asymmetric carbon atom. The last combination can also be consideredthat only a molecule having a polymerizable group and containing noasymmetric carbon atom functions as a discotic liquid crystal molecule,while a molecule containing asymmetric carbon atom and having nopolymerizable group functions as a chiral agent (described below).

The discotic liquid crystal molecule having no polymerizable group isobtained by replacing the polymerizable group (Q) of the above-describedpolymerizable discotic liquid crystal molecule with hydrogen or an alkylgroup. Accordingly, the discotic liquid crystal molecule having nopolymerizable group preferably is a compound represented by thefollowing formula.

D(—L—R)_(n)

in which D is a discotic core; L is a divalent linking group; R ishydrogen or an alkyl group; and n is an integer of 4 to 12.

Examples of the discotic cores are the same as the examples of the coresin the polymerizable discotic liquid crystal molecule, except that LQ orQL is replaced with LR or RL.

Examples of the divalent linking groups are also the same as theexamples of the linking groups in the polymerizable discotic liquidcrystal molecule.

The alkyl group of R contains preferably 1 to 40 carbon atoms, and morepreferably 1 to 30 carbon atoms. An alkyl group preferably has a chainstructure rather than a cyclic structure. An alkyl group having astraight chain (normal alkyl group) is preferred to a branched alkylgroup. R preferably is hydrogen or a normal alkyl group having 1 to 30carbon atoms.

In place of introducing asymmetric carbon atom into the divalent linkinggroup of the discotic liquid crystal molecule, the discotic liquidcrystal molecules can also be spirally twisted by adding an opticalactive compound containing asymmetric carbon atom (chiral agent) intothe optically anisotropic layer. Various natural or synthetic opticalactive compounds can be used as the chiral agent. The chiral agent canhave a polymerizable group, which is the same as or similar to thepolymerizable group of the discotic liquid crystal compound. Thediscotic liquid crystal molecules are fixed in the optically anisotropiclayer by a polymerization reaction after the molecules are essentiallyvertically (homogeneously) aligned. The chiral agent having apolymerizable group can also be fixed by the same or a similarpolymerization reaction.

The optically anisotropic layer can further contain a fluorinecontaining surface active agent or a cellulose ester, which has afunction of uniformly and essentially vertically (homogeneously)aligning discotic liquid crystal molecules placed near an interfacebetween the layer and the air.

The fluorine containing surface active agent comprises a hydrophobicgroup containing fluorine, a nonionic, anionic, cationic or amphoterichydrophilic group and an optional linking group.

The fluorine containing surface active agent comprising onehydrophobic-group and one hydrophilic group is represented by thefollowing formula.

Rf—L⁵—Hy

in which Rf is a monovalent hydrocarbon group substituted with fluorine;L⁵ is a single bond or divalent linking group; and Hy is a hydrophobicgroup.

Rf in the formula functions as a hydrophobic group. The hydrocarbongroup preferably is an alkyl group or an aryl group. The alkyl grouppreferably has 3 to 30 carbon atoms. The aryl group preferably has 6 to30 carbon atoms.

All or a part of hydrogen atoms contained in the hydrocarbon group issubstituted with fluorine. At least 50% of hydrogen atomss arepreferably substituted with fluorine. More preferably at least 60%,further preferably at least 70%, and most preferably at least 80% ofhydrogen atoms are substituted with fluorine.

The other hydrogens may be substituted with other halogen atoms (e.g.,chlorine, bromine).

Examples of Rf are shown below.

Rf1: n—C₈F₁₇—

Rf2: n—C6F₁₃—

Rf3: Cl—(CF₂—CFCl)₃—CF₂—

Rf4: H—(CF₂)₈—

Rf5: H—(CF₂)₁₀—

Rf6: n—C₉F₁₉—

Rf7: Pentafluorophenyl

Rf8: n—C₇F₁₅—

Rf9: Cl—(CF₂—CFCl)₂—CF₂—

Rf10: H—(CF₂)₄—

Rf11: H—(CF₂)₆—

Rf12: Cl—(CF₂)₆—

Rf13: C₃F₇—

In the formula, the divalent linking group is preferably selected fromthe group consisting of an alkylene group, an arylene group, a divalentheterocyclic group, —CO—, —NR—(in which R is hydrogen or an alkyl grouphaving 1 to 5 carbon atoms), —O—, —SO₂—and a combination thereof.

Examples of L⁴ in the formula are shown below. In the followingexamples, the left side is attached to a hydrophobic group (Rf) and theright side is attached to a hydrophilic group (Hy). AL means an alkylenegroup, AR means an arylene group, and Hc means a heterocyclic group. Thealkylene group, the arylene group and the heterocyclic group may have asubstituent group (e.g., an alkyl group).

L0: a single bond

L51: —SO₂—NR—

L52: —AL—O—

L53: —CO—NR—

L54: —AR—O—

L55: —SO₂—NR—AL—CO—O—

L56: —CO—O—

L57: —SO₂—NR—AL—O—

L58: —SO₂—NR—AL—

L59: —CO—NR—AL—

L60: AL¹—O—AL²—

L61: —Hc—AL—

L62: —SO₂—NR—AL¹—O—AL²—

L63: —AR—

L64: —O—AR—SO₂—NR—AL—

L65: —O—AR—SO₂—NR—

L66: —O—AR—O—

Hy in the formula is a nonionic hydrophilic group, an anionichydrophilic group, a cationic hydrophilic group or a combination thereof(an amphoteric hydrophilic group). A nonionic hydrophilic group isparticularly preferred.

Examples of Hy are shown below.

Hy1: —(CH₂CH₂O)_(n)—H (n: an integer of 5 to 30)

Hy2: —(CH₂CH₂O)_(n)—R¹ (n: an integer of 5 to 30, R¹: an alkyl grouphaving 1 to 6 carbon atoms)

Hy3: —(CH₂CHOHCH₂)_(n)—H (n: an integer of 5 to 30)

Hy4: —COOM (M: hydrogen, an alkali metal atom or dissociated)

Hy5: —SO₃M (M: hydrogen, an alkali metal atom or dissociated)

Hy6: —(CH₂CH₂O)_(n)—CH₂CH₂CH₂—SO₃M (n: an integer of 5 to 30, M;hydrogen or an alkali metal atom)

Hy7: —OPO(OH)₂

Hy8: —N⁺(CH₃)₃.X⁻ (X: a halogen-atom)

Hy9: —COONH₄

The nonionic hydrophilic groups (Hy1, Hy2, Hy3) are preferred, and thehydrophilic group consisting of polyethylene oxide (Hy1) is particularlypreferred.

The fluorine containing surface active agent may have two or morehydrophobic groups containing fluorine or two or more hydrophilicgroups. Two or more fluorine containing surface active agents can beused in combination.

The surface active agents are described in various documents, such asHiroshi Horiguchi, New Surface Active Agents, Sankyo Shuppan, 1975(written in Japanese), M. J. Schick, Nonionic Surfactants, MarcellDekker Inc., New York, 1967 and Japanese Patent Provisional PublicationNo. 7(1995)-13293.

The fluorine containing surface active agent is used in an amount of0.01 to 30 wt. % based on the amount of the discotic liquid crystalmolecules. The amount is preferably in the range of 0.05 to 10 wt. %,and more preferably in the range of 0.1 to 5 wt. %.

The cellulose ester preferably is a cellulose ester of a lower fattyacid.

The term “lower fatty acid” of the cellulose ester means a fatty acidhaving 1 to 6 carbon atoms. The lower fatty acid preferably has 2 to 5carbon atoms, and more preferably has 2 to 4 carbon atoms. The fattyacid may have a substituent group (e.g., hydroxyl). Two or more fattyacids may form an ester with cellulose acetate. Examples of thecellulose esters of the lower fatty acids include cellulose acetate,cellulose propionate, cellulose butyrate, cellulose hydroxypropionate,cellulose acetate propionate and cellulose acetate butyrate. Celluloseacetate butyrate is particularly preferred. Butyric acid content of thecellulose acetate butyrate is preferably not less than 30%, morepreferably in the range of 30 to 80%. Acetic acid content of thecellulose acetate butyrate is preferably less than 30%, and morepreferably in the range of 1 to 30%.

The coating amount of the cellulose ester is preferably in the range of0.005 to 0.5 g per m², more preferably in the range of 0.01 to 0.45 gper m², further preferably in the range of 0.02 to 0.4 g per m², andmost preferably in the range of 0.03 to 0.35 g per m². The amount of thecellulose ester is also preferably in the range of 0.1 to 5 wt. % basedon the amount of the discotic liquid crystal molecule.

An optically anisotropic layer can be formed by coating a solutioncontaining the discotic liquid crystal molecule and optional componentssuch as the chiral agent, the above-mentioned additive (a fluorinecontaining surface active agent, a cellulose ester), a polymerizationinitiator (described below) on an orientation layer.

A solvent for the preparation of the solution preferably is an organicsolvent. Examples of the organic solvents include amides (e.g.,dimethylformamide), sulfoxides (e.g., dimethylsulfoxide), heterocycliccompounds (e.g., pyridine), hydrocarbons (e.g., benzene, hexane), alkylhalides (e.g., chloroform, dichloromethane), esters (e.g., methylacetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone)and ethers (e.g., tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halidesand ketones are preferred. Two or more organic solvents can be used incombination.

The solution can be coated according to a conventional coating methodsuch as an extrusion coating method, a direct gravure coating method, areverse gravure coating method, a die coating method or a bar coatingmethod.

The aligned discotic liquid crystal molecules are preferably fixed whilekeeping the essentially vertical (homogeneous) alignment. The discoticliquid crystal molecules are fixed preferably by a polymerizationreaction of the polymerizable groups (Q) in the molecules. Thepolymerization reaction can be classified a thermal reaction using athermal polymerization initiator and a photo reaction using a photopolymerization initiator. A photo polymerization reaction is preferred.

Examples of the photo polymerization initiators include α-Carbonylcompounds (described in U.S. Pat. Nos. 2,367,661, 2,367,670), acyloinethers (described in U.S. Pat. No. 2,448,828), α-hydrocarbon substitutedacyloin compounds (described in U.S. Pat. No. 2,722,512), polycyclicquinone compounds (described in U.S. Pat. Nos. 2,951,758, 3,046,127),combinations of triarylimidazoles and p-aminophenyl ketones (describedin U.S. Pat. No. 3,549,367), acridine or phenazine compounds (describedin Japanese Patent Provisional Publication No. 60(1985)-105667 and U.S.Pat. No. 4,239,850) and oxadiazole compounds (described in U.S. Pat. No.4,212,970).

The amount of the photo polymerization initiator is preferably in therange of 0.01 to 20 wt. %, and more preferably in the range of 0.5 to 5wt. % based on the solid content of the coating solution of the layer.

The light irradiation for the photo polymerization is preferablyconducted by an ultraviolet ray.

The exposure energy is preferably in the range of 20 to 5,000 mJ per cm²and more preferably in the range of 100 to 800 mJ per cm². The lightirradiation can be conducted while heating the layer to accelerate thephoto polymerization reaction.

The optically anisotropic layer has a thickness preferably in the rangeof 0.1 to 50 μm, more preferably 1 to 30 μm, and most preferably in therange of 5 to 20 μm. In the case that two optical compensatory sheetsare used in a liquid crystal display, the preferred thickness of thelayer is half of the preferred thickness (described above) in the casethat one optical compensatory sheet is used in a liquid crystal display.

The discotic liquid crystal molecules in the optically anisotropic layerare aligned at an average inclined angle in the range of 50° to 90°. Theinclined angle is preferably uniform. However, the inclined angle can bechanged if the angle is continuously changed along the thickness of theoptical anisotropic layer.

The twist angle of the discotic liquid crystal molecules is preferablysimilar to a twist angle of a liquid crystal cell of an STN mode, whichis usually in the range of 180° to 360°, and preferably in the range of180° to 270°. The difference between the twist angles is preferably notlarger than 10°. In the case that one optical compensatory sheet is usedin a liquid crystal display, the twist angle of the discotic liquidcrystal molecules is preferably in the range of 180° to 360°. In thecase that two optical compensatory sheets are used in a liquid crystaldisplay, the twist angle of the discotic liquid crystal molecules ispreferably in the range of 90° to 180°. In a liquid crystal display ofan STN mode, a wavelength dependency of the birefringence (Δn(λ)) of anoptically anisotropic layer is preferably similar to a wavelengthdependency of the birefringence of a liquid crystal cell of an STN mode.

[Liquid Crystal Display]

The present invention is particularly effective in a liquid crystaldisplay of an STN mode.

The liquid crystal display of an STN mode comprises a liquid crystalcell of an STN mode, two polarizing elements arranged on each side ofthe liquid crystal cell, and one or two optical compensatory sheetsarranged between the liquid crystal cell and the polarizing element.

The alignment of rod-like liquid crystal molecule in the liquid crystalcell and the alignment of the discotic liquid crystal molecules in theoptical compensatory sheet is preferably so adjusted that a director ofa rod-like liquid crystal molecule adjacent to the optical compensatorysheet is the essentially same direction of a director of the discoticliquid crystal molecule adjacent to the liquid crystal cell. Thedirector of the rod-like liquid crystal molecule means the direction ofthe long axis of the rod-like molecule. The director of the discoticliquid crystal molecule means the direction of a normal line of thediscotic core plane. The essentially same direction means that the anglebetween the directors viewed along a normal line of the liquid crystalcell.

The transparent substrate of the optical compensatory sheet can be usedas a protective film of a polarizing plate (on the side facing theliquid crystal cell). In this case, a slow axis (direction showing themaximum refractive index) of the transparent substrate is preferably soarranged that the slow axis is essentially perpendicular or parallel tothe transmission axis (direction showing the maximum transmittance) ofthe polarizing plate. The term “essentially perpendicular or parallel”means that a margin for error based on the exact angle is in the rangeof ±10°.

EXAMPLE 1

A triacetyl cellulose film (thickness: 100 μm, size: 270 mm×100 mm, FujiTac, Fuji Photo Film Co., Ltd.) was used as a transparent substrate.

A denatured polyvinyl alcohol (PV1) having a hydrocarbon group wasdissolved in a mixture of methanol and water (volume ratio: 50/50) toprepare a 5 wt. % solution. The solution was coated on the transparentsubstrate by using a bar coater (thickness: 1 μm), and air-dried at 60°C. for 2 minutes. The surface was subjected to a rubbing treatment toform an orientation layer.

The following coating solution was coated on the orientation layeraccording to an extrusion method.

Coating Solution for Optically Anisotropic Layer

The following discotic liquid crystal compound (1)

80 weight parts

The following discotic liquid crystal compound (2)

20 weight parts

The following fluorine containing surface active agent

0.1 weight part

A photopolymerization initiator (Irgacure 907, Ciba-Geigy)

0.2 weight part

Methyl ethyl ketone

185 weight parts

The coated layer was heated at 130° C. to essentially vertically alignthe discotic liquid crystal compound. The layer was irradiated with anultraviolet ray for 4 seconds to polymerize the discotic liquid crystalcompound and to fix the alignment. Thus an optical compensatory sheetwas prepared. In the optically anisotropic layer, the discotic liquidcrystal molecules are twisted, and are essentially vertically aligned.

Polarized light was incident on the transparent substrate of the opticalcompensatory sheet along a direction of 45° based on the rubbingdirection of the orientation layer. Polarization of transmitted lightwas analyzed (Multi Chanel Photo Analizer, Ohtsuka Electronics Co.,Ltd.). As a result, the twist angle was in the range of 230° to 250°.

Another optical compensatory sheet was prepared in the same mannerexcept that the discotic liquid crystal compound (2), which functions asa chiral agent, was not used. In the optically anisotropic layer, thediscotic liquid crystal molecules are not twisted, but are essentiallyvertically aligned. The retardation in plane (Re). of the sheet wasmeasured to determine dependency of birefringence on a viewing angle.The average inclined angle was obtained by the dependency ofbirefringence. As a result, the average inclined angle was in the rangeof 70° to 85°.

Further, an antiparallel cell was-prepared by using a horizontalorientation layer. The discotic liquid crystal compounds (1) and (2)were inserted into the antiparallel cell. The retardation in plane (Re)of the obtained liquid crystal cell was measured by using anellipsometer. The retardation was divided by the thickness of the cellto determine Δn of 0.07.

EXAMPLE 2

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 1, except that a denatured polyvinyl alcohol (PV25)was used in place of the denatured polyvinyl alcohol (PV1). The averageinclined angle of the discotic liquid crystal molecules was 70°.

EXAMPLE 3

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 1, except that a denatured polyvinyl alcohol (PV40)was used in place of the denatured polyvinyl alcohol (PV1). The averageinclined angle of the discotic liquid crystal molecules was 60°.

EXAMPLE 4

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 1, except that a denatured polyvinyl alcohol (PV53)was used in place of the denatured polyvinyl alcohol (PV1). The averageinclined angle of the discotic liquid crystal molecules was 75°.

COMPARISON EXAMPLE 1

A commercially available inorganic material for a vertical orientationlayer (EXP-OA004, Nissan Chemical Industries Ltd.) was diluted withmethanol to a solid content of 2 wt. %. The diluted material was coatedon a glass plate by using a bar coater (thickness: 0.4 μm), and dried at140° C. to form an inorganic orientation layer. The orientation layerwas subjected to a rubbing treatment.

Two antiparallel cells were prepared. A rod-like liquid crystal compound(MBBA) was inserted into one cell. A discotic liquid crystal compound(obtained by removing methyl ethyl ketone from the coating solution foroptically anisotropic layer used in Example 1) was inserted into theother cell.

The alignment of the liquid crystal molecule was examined. The cellcontaining the rod-like liquid crystal molecules shows a nematicalignment of the molecules, which is vertical to a glass plate. On theother hand, the average inclined angle of the discotic liquid crystalmolecules was 30°. Therefore, the discotic liquid crystal molecules werenot vertically (50° to 90°) aligned.

The tested material for a vertical orientation layer (EXP-OA004, NissanChemical Industries Ltd.) is commercially available, and is used forpreparation of an orientation layer for a rod-like liquid crystalcompound. The other commercially available materials for a verticalorientation layer were also tested in the same manner. As a result,vertical orientation layers for a rod-like liquid crystal compound werenot effective in aligning a discotic liquid crystal compound vertically.

EXAMPLE 5

A liquid crystal display of an STN mode shown in FIG. 3(e) was preparedby using an optical compensatory sheet prepared in Example 1. Along theinterface between the liquid crystal cell and the optical compensatorysheet, the director of the discotic liquid crystal molecule of the sheetwas arranged at the same direction of the director of the rod-likeliquid crystal molecule of the cell. The angle between the absorbingaxis of the upper polarizing plate and the director of the rod-likeliquid crystal molecule adjacent to the upper orientation layer wasadjusted to 45°. The absorbing axis of the upper polarizing plate wasperpendicular to the absorbing axis of the lower polarizing plate.

A voltage was applied to the obtained liquid crystal display of an STNmode to display an image of a normally black mode. The viewing angleshowing a contrast ratio of not less than 5 was measured. As a result,leftward and rightward viewing angle was 120° or more, and upward anddownward viewing angle was 150° or more. Further, a blue or yellow colorwas not observed in the displayed image.

EXAMPLE 6

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 1, except that the following coating solution forthe optically anisotropic layer was used. The results were the same asthe results of Example 1.

Coating Solution for Optically Anisotropic Layer

The following discotic liquid crystal compound (3)

63 weight parts

The discotic liquid crystal compound (2) used in Example 1

27 weight parts

The following polymerizable plasticizer

10 weight parts

A photopolymerization initiator (Irgacure 907, Ciba-Geigy)

1 weight part

Cellulose acetate butyrate (CAB551-0.2, Eastman Chemical)

0.5 weight part

Methyl ethyl ketone

184.5 weight parts

EXAMPLE 7

A triacetyl cellulose film (thickness: 100 μm, size: 270 mm×100 mm, FujiTac, Fuji Photo Film Co., Ltd.) was used as a transparent substrate.

A denatured polyvinyl alcohol (PV101) having a steroid hydrocarbon groupwas dissolved in a mixture of methanol and water (volume ratio: 50/50)to prepare a 5 wt. % solution. The solution was coated on thetransparent substrate by using a bar coater (thickness: 1 μm), andair-dried at 80°C. for 10 minutes. The surface was subjected to arubbing treatment to form an orientation layer.

An optically anisotropic layer was formed on the orientation layer inthe same manner as in Example 1 to prepare an optical compensatorysheet.

Polarized light was incident on the transparent substrate of the opticalcompensatory sheet along a direction of 45° based on the rubbingdirection of the orientation layer. Polarization of transmitted lightwas analyzed (Multi Chanel Photo Analizer, Ohtsuka Electronics Co.,Ltd.). As a result, the twist angle was in the range of 230° to 250°.

Another optical compensatory sheet was prepared in the same mannerexcept that the discotic liquid crystal compound (2), which functions asa chiral agent was not used. In the optically anisotropic layer, thediscotic liquid crystal molecules are not twisted, but are essentiallyvertically aligned. The retardation in plane (Re) of the sheet wasmeasured to determine dependency of birefringence on a viewing angle.The average inclined angle was obtained by the dependency ofbirefringence. As a result, the average inclined angle was in the rangeof 70° to 85°.

Further, an antiparallel cell was prepared by using a horizontalorientation layer. The discotic liquid crystal compounds (1) and (2)were inserted into the antiparallel cell. The retardation in plane (Re)of the obtained liquid crystal cell was measured by using anellipsometer. The retardation was divided by the thickness of the cellto determine Δn of 0.07.

EXAMPLE 8

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 7, except that a denatured polyvinyl alcohol(PV125) was used in place of the denatured polyvinyl alcohol (PV101).The average inclined angle of the discotic liquid crystal molecules was70°.

EXAMPLE 9

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 7, except that a denatured polyvinyl alcohol(PV140) was used in place of the denatured polyvinyl alcohol (PV101).The average inclined angle of the discotic liquid crystal molecules was60°.

EXAMPLE 10

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 7, except that a denatured polyvinyl alcohol(PV153) was used in place of the denatured polyvinyl alcohol (PV101).The average inclined angle of the discotic liquid crystal molecules was75°.

EXAMPLE 11

A liquid crystal display of an STN mode shown in FIG. 3(e) was preparedby using an optical compensatory sheet prepared in Example 7. Along theinterface between the liquid crystal cell and the optical compensatorysheet, the director of the discotic liquid crystal molecule of the sheetwas arranged at the same direction of the director of the rod-likeliquid crystal molecule of the cell. The angle between the absorbingaxis of the upper polarizing plate and the director of the rod-likeliquid crystal molecule adjacent to the upper orientation layer wasadjusted to 45°. The absorbing axis of the upper polarizing plate wasperpendicular to the absorbing axis of the lower polarizing plate.

A voltage was applied to the obtained liquid crystal display of an STNmode to display an image of a normally black mode. The viewing angleshowing a contrast ratio of not less than 5 was measured. As a result,leftward and rightward viewing angle was 120° or more, and upward anddownward viewing angle was 150° or more. Further, a blue or yellow colorwas not observed in the displayed image.

EXAMPLE 12

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 7, except that the following coating solutionoptically anisotropic layer was used. The results were the same as theresults of Example 7.

Coating Solution for Optically Anisotropic Layer

The discotic liquid crystal compound (3) used in Example 6

63 weight parts

The discotic liquid crystal compound (2) used in Example 1

22 weight parts

The polymerizable plasticizer used in Example 6

10 weight parts

A photopolymerization initiator (Irgacure 907, Ciba-Geigy)

1 weight part

Cellulose acetate butyrate (CAB551-0.2, Eastman Chemical)

0.5 weight part

Methyl ethyl ketone

184.5 weight parts

EXAMPLE 13

A triacetyl cellulose film (thickness: 100 μm, size: 270 mm×100 mm, FujiTac, Fuji Photo Film Co., Ltd.) was used as a transparent substrate.

A denatured polyvinyl alcohol (PV201) containing fluorine atoms wasdissolved in a mixture of methanol and water (volume ratio: 50/50) toprepare a 5 wt. % solution. The solution was coated on the transparentsubstrate by using a bar coater (thickness: 1 μm), and air-dried at 60°C. for 2 minutes. The surface was subjected to a rubbing treatment toform an orientation layer.

An optically anisotropic layer was formed on the orientation layer inthe same manner as in Example 1 to prepare an optical compensatorysheet.

Polarized light was incident on the transparent substrate of the opticalcompensatory sheet along a direction of 45° based on the rubbingdirection of the orientation layer. Polarization of transmitted lightwas analyzed (Multi Chanel Photo Analizer, Ohtsuka Electronics Co.,Ltd.). As a result, the twist angle was in the range of 230° to 250°.

Another optical compensatory sheet was prepared in the same mannerexcept that the discotic liquid crystal compound (2), which functions asa chiral agent was not used. In the optically anisotropic layer, thediscotic liquid crystal molecules are not twisted, but are essentiallyvertically aligned. The retardation in plane (Re) of the sheet wasmeasured to determine dependency of birefringence on a viewing angle.The average inclined angle was obtained by the dependency ofbirefringence. As a result, the average inclined angle was in the rangeof 70° to 85°.

Further, an antiparallel cell was prepared by using a horizontalorientation layer. The discotic liquid crystal compounds (1) and (2)were inserted into the antiparallel cell. The retardation in plane (Re)of the obtained liquid crystal cell was measured by using anellipsometer. The retardation was divided by the thickness of the cellto determine Δn of 0.07.

EXAMPLE 14

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 13, except that a denatured polyvinyl alcohol(PV251) was used in place of the denatured polyvinyl alcohol (PV201).The average inclined angle of the discotic liquid crystal molecules was70°.

EXAMPLE 15

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 13, except that a denatured polyvinyl alcohol(PV207) was used in place of the denatured polyvinyl alcohol (PV201).The average inclined angle of the discotic liquid crystal molecules was60°.

EXAMPLE 16

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 13, except that a denatured polyvinyl alcohol(PV216) was used in place of the denatured polyvinyl alcohol (PV201).The average inclined angle of the discotic liquid crystal molecules was75°.

EXAMPLE 17

A liquid crystal display of an STN mode shown in FIG. 3(e) was preparedby using an optical compensatory sheet prepared in Example 13. Along theinterface between the liquid crystal cell and the optical compensatorysheet, the director of the discotic liquid crystal molecule of the sheetwas arranged at the same direction of the director of the rod-likeliquid crystal molecule of the cell. The angle between the absorbingaxis of the upper polarizing plate and the director of the rod-likeliquid crystal molecule adjacent to the upper orientation layer wasadjusted to 45°. The absorbing axis of the upper polarizing plate wasperpendicular to the absorbing axis of the lower polarizing plate.

A voltage was applied to the obtained liquid crystal display of an STNmode to display an image of a normally black mode. The viewing angleshowing a contrast ratio of not less than 5 was measured. As a result,leftward and rightward viewing angle was 120° or more, and upward anddownward viewing angle was 150° or more. Further, a blue or yellow colorwas not observed in the displayed image.

EXAMPLE 18

An optical compensatory sheet was prepared and evaluated in the samemanner as in Example 13, except that the following coating solutionoptically anisotropic layer was used. The results were the same as theresults of Example 13.

Coating Solution for Optically Anisotropic Layer

The discotic liquid crystal compound (3) used in Example 6

63 weight parts

The discotic liquid crystal compound (2) used in Example 1

22 weight parts

The polymerizable plasticizer used in example 6

10 weight parts

A photopolymerization initiator (Irgacure 907, Ciba-Geigy)

1 weight part

Cellulose acetate butyrate (CAB551-0.2, Eastman Chemical)

0.5 weight part

Methyl ethyl ketone

184.5 weight parts

We claim:
 1. An orientation layer provided on a support, saidorientation layer having a function of aligning liquid crystal, whereinthe orientation layer comprises a denatured polyvinyl alcohol having ahydrocarbon group containing 10 to 100 carbon atoms.
 2. A method ofalignment of discotic liquid crystal molecules, which comprises formingan optically anisotropic layer comprising discotic liquid crystalmolecules on an orientation layer comprising a denatured polyvinylalcohol having a hydrocarbon group containing 10 to 100 carbon atoms toalign the discotic liquid crystal molecules at an average inclined anglein the range of 50° to 90°.
 3. An optical compensatory sheet comprisinga transparent substrate, an orientation layer and an opticallyanisotropic layer in order, said optically anisotropic layer comprisingdiscotic liquid crystal molecules, wherein the orientation layercomprises a denatured polyvinyl alcohol having a hydrocarbon groupcontaining 10 to 100 carbon atoms, said discotic liquid crystalmolecules being aligned at an average inclined angle in the range of 50°to 90°.
 4. The optical compensatory sheet as defined in claim 3, whereinthe denatured polyvinyl alcohol comprises hydrocarbon repeating units inan amount of 2 to 80 mol %, said repeating units having a hydrocarbongroup containing 10 to 100 carbon atoms.
 5. The optical compensatorysheet as defined in claim 3, wherein the-hydrocarbon group has a steroidstructure.
 6. The optical compensatory sheet as defined in claim 3,wherein the discotic liquid crystal molecules are twisted at an averagetwist angle in the range of 90° to 360°.
 7. The optical compensatorysheet as defined in claim 3, wherein the discotic liquid crystalmolecules are polymerized.
 8. The optical compensatory sheet as definedin claim 3, wherein the discotic liquid crystal molecules contain anasymmetric carbon atom.
 9. The optical compensatory sheet as defined inclaim 3, wherein the optically anisotropic layer further contains achiral agent.
 10. A liquid crystal display comprising a liquid crystalcell of an STN mode, two polarizing elements arranged on each side ofthe liquid crystal cell and one or two optical compensatory sheetsarranged between the liquid crystal cell and the polarizing elements,wherein the optical compensatory sheet comprises a transparentsubstrate, an orientation layer and an optically anisotropic layer inorder, said transparent substrate being adjacent to the polarizingelement, said optically anisotropic layer comprising discotic liquidcrystal molecules, said orientation layer comprising a denaturedpolyvinyl alcohol having a hydrocarbon group containing 10 to 100 carbonatoms, and said discotic liquid crystal molecules being aligned at anaverage inclined angle in the range of 50° to 90°.